U.S. patent application number 12/360428 was filed with the patent office on 2010-07-29 for proactive scheduling methods and apparatus to enable peer-to-peer communication links in a wireless ofdma system.
This patent application is currently assigned to MOTOROLA, INC.. Invention is credited to Michael H. BAKER, Jeffrey D. BONTA, George CALCEV, Nitin R. MANGALVEDHE, James P. MICHELS, Nathan J. SMITH.
Application Number | 20100189048 12/360428 |
Document ID | / |
Family ID | 42354091 |
Filed Date | 2010-07-29 |
United States Patent
Application |
20100189048 |
Kind Code |
A1 |
BAKER; Michael H. ; et
al. |
July 29, 2010 |
PROACTIVE SCHEDULING METHODS AND APPARATUS TO ENABLE PEER-TO-PEER
COMMUNICATION LINKS IN A WIRELESS OFDMA SYSTEM
Abstract
Systems, methods and apparatus are provided for scheduling
resources in Orthogonal Frequency-Division Multiple Access (OFDMA)
communication networks for "direct link" or peer-to-peer
communications among stations operating therein so that OFDMA
resources can be allocated to a transmitter station for a
peer-to-peer communication session with a receiver station such
that near-far issues caused by peer-to-peer communication are
reduced/avoided. The disclosed technologies can prevent
peer-to-peer communication links using different sub-channels
within the same time slot from creating near-far issues for other
receiver stations that are within communication range.
Inventors: |
BAKER; Michael H.;
(Elmhurst, IL) ; BONTA; Jeffrey D.; (Arlington
Heights, IL) ; CALCEV; George; (Hoffman Estates,
IL) ; MANGALVEDHE; Nitin R.; (Hoffman Estates,
IL) ; MICHELS; James P.; (Lake Zurich, IL) ;
SMITH; Nathan J.; (Urbana, IL) |
Correspondence
Address: |
MOTOROLA, INC.
1303 EAST ALGONQUIN ROAD, IL01/3RD
SCHAUMBURG
IL
60196
US
|
Assignee: |
MOTOROLA, INC.
Schaumburg
IL
|
Family ID: |
42354091 |
Appl. No.: |
12/360428 |
Filed: |
January 27, 2009 |
Current U.S.
Class: |
370/329 ;
375/260 |
Current CPC
Class: |
H04L 5/0073 20130101;
H04L 5/0082 20130101; H04L 5/0094 20130101; H04L 5/0037 20130101;
H04L 5/006 20130101 |
Class at
Publication: |
370/329 ;
375/260 |
International
Class: |
H04W 72/04 20090101
H04W072/04 |
Claims
1. A method for scheduling Orthogonal Frequency-Division Multiple
Access (OFDMA) resources allocated to a transmitter station for a
peer-to-peer communication session with a receiver station, the
method comprising: maintaining, at the base station, a resource
allocation map comprising: particular OFDMA resources of an OFDMA
frame that have been allocated to particular stations; and
generating, at a base station, a request for information with
respect to selected OFDMA resources; receiving at the base station,
a resource request message (RRM) from the transmitter station to
request allocation of some of the OFDMA resources for the
peer-to-peer communication session with the receiver station; and
processing, at the base station, to determine specific ones of the
OFDMA resources to be allocated to the transmitter station for the
peer-to-peer communication session with the receiver station.
2. A method according to claim 1, wherein each of the OFDMA
resources is a OFDMA frequency sub-channel within an OFDMA time
slot, and wherein the request for information with respect to
selected OFDMA resources comprises: a resource map information
element (RMIE), wherein the RMIE comprises: a Partial Resource
Allocation Map (PRAM), comprising: selected OFDMA resources of the
OFDMA frame that the base station is requesting more information
about; an indicator that a radio frequency (RF) quality metric is
to be measured with respect to the selected OFDMA resources; a
number of first metric measurements being requested with respect to
the selected OFDMA resources; and a first metric categories field
which identifies one or more first metric categories a station is
to report with respect to the selected OFDMA resources, and further
comprising: broadcasting the RMIE, from the base station to
recipient stations including the transmitter station, to request
first metric measurement information from the recipient stations
based on information specified in the PRAM; receiving, at the
recipient stations including the transmitter station, the RMIE, and
measuring first metric with respect to some of the selected OFDMA
resources specified in the PRAM; generating, at the recipient
stations including the transmitter station, a resource map response
message (RMRM) comprising information regarding first metric
measurement with respect to some of the selected OFDMA resources,
wherein the RMRM generated by the transmitter station comprises a
first RMRM; transmitting, to the base station, the respective RMRMs
generated by each of the recipient stations including the first
RMRM generated by the transmitter station, and the resource request
message (RRM) from the transmitter station to request allocation of
some of the OFDMA resources for the peer-to-peer communication
session with the receiver station.
3. A method according to claim 2, wherein the specific ones of the
OFDMA resources allocated to the transmitter station each comprise:
an allocated OFDMA sub-channel within a particular OFDMA time slot,
and wherein the specific ones of the OFDMA resources are allocated
such that other stations communicating over different OFDMA
sub-channels of the particular OFDMA time slots will not cause
near-far problems for the receiver station, and communications by
the transmitter station using the specific ones of the OFDMA
resources will not cause near-far problems for the other stations
communicating over different OFDMA sub-channels of the particular
OFDMA time slots.
4. A method according to claim 1, wherein the peer-to-peer
communication session between the transmitter station and the
receiver station takes place in an OFDMA cell defined by the base
station, and further comprising: dynamically adjusting the resource
measurement information of the RMIE at the base station as traffic
characteristics change within the OFDMA cell.
5. A method according to claim 2, wherein the resource request
message (RRM) transmitted from the transmitter station to request
allocation of some of the OFDMA resources for the peer-to-peer
communication session with the receiver station, comprises: an
indicator which indicates the type of peer-to-peer communication
session the transmitter station would like to set up with the
receiver station including information regarding QoS requirements
for that type of peer-to-peer communication session; information
regarding the station type of the transmitter station; and
information regarding the size of the packet to be transmitted by
the transmitter station.
6. A method according to claim 2, wherein the step of measuring
first metric with respect to some of the selected OFDMA resources
specified in the PRAM, comprises: decoding, at the recipient
stations including the transmitter station, the PRAM; starting a
resource measurement period timer at each of the recipient stations
including the transmitter station; monitoring, at the recipient
stations including the transmitter station, an OFDMA channel for an
OFDMA frame; selecting, at the recipient stations including the
transmitter station, particular ones of the selected OFDMA
resources from the PRAM; and measuring, at the recipient stations
including the transmitter station, the first metric with respect to
each of the particular ones of the selected OFDMA resources that
are selected by that particular recipient station.
7. A method according to claim 6, wherein the step of generating,
at each of the recipient stations including the transmitter
station, a resource map response message (RMRM), comprises:
sorting, at each of the recipient stations including the
transmitter station, measured first metric for each of the
particular ones of the selected OFDMA resources into one of a
plurality of first metric categories that categorize the particular
ones of the selected OFDMA resources based on measured first
metric, wherein the plurality of first metric categories comprise:
a high first metric category that includes information regarding
peer stations that cause high level interference; a medium first
metric category that includes information regarding peer stations
that cause medium level interference, and a low first metric
category that includes information regarding peer stations that
cause low level interference; generating, at each of the recipient
stations including the transmitter station, a partial resource
measurement map (PRMM) comprising the plurality of first metric
categories, wherein each of the first metric categories includes
first metric measurement information regarding some of the
particular ones of the selected OFDMA resources; and generating, at
each of the recipient stations including the transmitter station
upon expiration of the resource measurement period, a resource map
response message (RMRM) comprising the PRMM as determined by that
particular station, wherein the RMRMs generated by the transmitter
station comprises the first RMRMs including first PRMMs.
8. A method according to claim 7, wherein each RMRM comprises: a
resource type field that specifies a type of resource that the
particular station is reporting in the RMRM; a total categories
field that specifies a total number of different first metric
categories being reported in the RMRM; and a partial resource
measurement map (PRMM) comprising: a plurality of first metric
categories each including information regarding first metric
measurements made by the particular station for selected ones of
the selected OFDMA resources specified in the PRAM, wherein the
plurality of first metric power categories specified in each PRMM
comprise: a high first metric category used to report high power
first metric measurements, a medium first metric category used to
report medium power first metric measurements, and a low first
metric category used to report low power first metric
measurements.
9. A method according to claim 8, wherein each of the first metric
categories comprise a plurality of fields used to report
information regarding first metric measurements by the particular
station for that first metric power category, the plurality of
fields comprising: a category identifier field that identifies the
particular first metric category; a number measured field that
specifies a number of first metric measurements that are included
for the particular first metric category, and a category MAP data
field that specifies particular resource locations in the resource
allocation map for the particular first metric category, wherein
each particular resource location is specified as at least one
specific sub-channels and at least one time slot.
10. A method according to claim 9, wherein the step of processing,
at the base station, the RMRMs to determine specific ones of the
OFDMA resources to be allocated to the transmitter station for the
peer-to-peer communication session with the receiver station,
comprises: receiving, at the base station, the first resource map
response message (RMRM) from the transmitter station; determining,
at the base station based on the RMM, a packet size the transmitter
station requests to transmit in the peer-to-peer communication
session with the receiver station; determining, at the base station
based on the one or more first PRMMs from the first RMRM, updated
peer station information for the transmitter station; and
scheduling a first OFDMA resource in a first OFDMA time slot for a
first transmission by the transmitter station to the receiver
station during the peer-to-peer communication session; and
scheduling other OFDMA resources in other OFDMA time slots for
other transmissions by high first metric peer stations of the
receiver station having high power first metric such that the first
transmission is received by the receiver station at a time when the
high first metric peer stations of the receiver station are not
transmitting so that the first transmission is isolated in the time
domain from the other transmissions by the high first metric peer
stations of the receiver station.
11. A method according to claim 10, wherein the step of
determining, at the base station based on the one or more first
PRMMs from the first RMRM, updated peer station information for the
transmitter station, comprises: extracting, at the base station
from the one or more first PRMMs that was received from the
transmitter station, information regarding first metric
measurements made by the transmitter station for the selected ones
of the selected OFDMA resources; using the resource allocation map
maintained at the base station to translate the selected ones of
the selected OFDMA resources into corresponding peer station
identification numbers; determining, at the base station, first
metric categories from the one or more first PRMMs for each of the
peer station indentification numbers, and assigning each particular
peer station identification number to one of: a high power first
metric transmitter peer list that specifies peer stations having
high power first metric, a low power first metric transmitter peer
list that specifies peer stations having low power first metric,
and a medium power first metric transmitter peer list that
specifies peer stations having medium power first metric; creating,
at the base station, an entry in a peer memory map (PMM) for the
transmitter station, wherein the PMM comprises a plurality of rows,
and a plurality of columns, the plurality of columns comprising: a
first column that lists peer station identification numbers
corresponding to peer-to-peer enabled stations including the
transmitter station and the receiver station, wherein each row
corresponds to entry for a particular peer-to-peer enabled station
that is identified in the first column by a particular peer station
identification number; a second column comprising the high power
first metric transmitter peer list that specifies peer stations
having high power first metric, wherein the second column lists
peer station identification numbers for peer stations of the
corresponding station in the first column; a third column
comprising the low power first metric transmitter peer list that
specifies peer stations having low power first metric, wherein the
third column lists peer station identification numbers for peer
stations of the corresponding station in the first column; and a
fourth column comprising the medium power first metric transmitter
peer list that specifies peer stations having medium power first
metric, wherein the fourth column lists peer station identification
numbers for peer stations of the corresponding station in the first
column.
12. A method according to claim 11, wherein the step of scheduling
comprises: processing, at the base station, the first PRMM provided
in the first RMRM and other PRMMs provided in other RMRMs from
other recipient stations, to generate: a high impact peer set that
identifies stations in the high power first metric transmitter peer
list of the transmitter station that are susceptible to near-far
issues when one station that belongs to the high impact peer set
transmits while another station that belongs to the high impact
peer set is receiving a different transmission from another station
that does not belong to the high impact peer set, and a low impact
peer set that identifies stations in the low power first metric
transmitter peer list of the transmitter station that are not
susceptible to near-far issues when one station that belongs to the
low impact peer set transmits while another station that belongs to
the low impact peer set is receiving a different transmission from
another station that does not belong to the low impact peer set;
using information in the resource allocation map, the high impact
peer set and the low impact peer set to determine preferred OFDMA
time slots (TSP) of the OFDMA frame and excluded OFDMA time slots
(TS.sub.x) of the OFDMA frame, and marking the preferred OFDMA time
slots (TS.sub.p) and excluded OFDMA time slots (TS.sub.x) in the
resource allocation map maintained at the base station; estimating,
at the base station, a resource allocation size (RAS) for the
peer-to-peer communication session between the transmitter station
and the receiver station; and determining, at the base station
based on the estimated RAS, a resource allocation comprising at
least one of the preferred OFDMA time slot (TS.sub.p) and at least
one sub-channel in that preferred OFDMA time slot (TS.sub.p) to
allocate for the peer-to-peer communication session between the
transmitter station and the receiver station.
13. A method according to claim 12, wherein the step of using
information in the resource allocation map, the high impact peer
set and the low impact peer set to determine preferred OFDMA time
slots (TS.sub.p) of the OFDMA frame and excluded OFDMA time slots
(TS.sub.x) of the OFDMA frame, and marking the preferred OFDMA time
slots (TS.sub.p) and excluded OFDMA time slots (TS.sub.x) in the
resource allocation map maintained at the base station, comprises:
marking, at the base station, any time slots allocated to peer
stations in a high impact peer set of the receiver station as
excluded OFDMA time slots (TS.sub.x) of the OFDMA frame; marking,
at the base station, any time slots allocated to peer stations in
the high impact peer set of the transmitter station as preferred
OFDMA time slots (TS.sub.p) of the OFDMA frame; and when the high
impact peer set of the transmitter station includes no peer
stations, marking, at the base station, any time slots allocated to
peer stations in a low impact peer set of the receiver station as
preferred OFDMA time slots (TS.sub.p) of the OFDMA frame.
14. A method according to claim 13, when an OFDMA time slot is
marked as being both an excluded time slot (TS.sub.x) and preferred
time slot (TSP), further comprising: marking the OFDMA time slot:
as a preferred OFDMA time slot (TSP) of the OFDMA frame when the
transmitter station is a member of the high impact peer set of the
receiver station, or as an excluded OFDMA time slot (TS.sub.x) of
the OFDMA frame when the transmitter station is not a member of the
high impact peer set of the receiver station.
15. A method according to claim 12, further comprising:
transmitting, from the base station to the transmitter station and
the receiver station, a resource grant message (RGM) to notify the
transmitter station and the receiver station of the resources
allocation to the transmitter station and the receiver station for
the peer-to-peer communication session between the transmitter
station and the receiver station.
16. A method according to claim 2, wherein the first metric
comprises a radio frequency (RF) quality metric.
17. A method according to claim 16, wherein the RF quality metric
comprises: Receive Signal Strength (RSS) power levels.
18. A method according to claim 16, wherein the RF quality metric
comprises: Signal-to-interference-plus-Noise Ratio (SINR).
19. A method according to claim 16, wherein the RF quality metric
comprises: Signal-to-Noise Ratio (SNR).
20. A method according to claim 16, wherein the RF quality metric
comprises: range.
21. A method according to claim 1, wherein the OFDMA frame
comprises: a downlink portion comprising downlink OFDMA resources
for downlink communications from the base station to stations, and
an uplink portion comprising uplink OFDMA resources for normal
uplink communications from the stations to the base station and for
direct peer-to-peer communication between stations and wherein the
resource allocation map comprises: designations of selected ones of
the downlink OFDMA resources presently allocated to stations for
downlink communications from the base station to stations, and
designations of selected ones of the uplink OFDMA resources
presently allocated to stations for normal uplink communications
from the stations to the base station and presently allocated for
direct peer-to-peer communication between stations in the uplink
portion of the OFDMA frame.
22. A method according to claim 21, wherein the uplink portion
comprises a dedicated zone, wherein the dedicated zone comprises
OFDMA resources reserved exclusively for direct station-to-station
communications such that normal uplink communications from the
stations to the base station can not be scheduled in the dedicated
zone.
23. A method according to claim 1, wherein the base station defines
a cell of an OFDMA communication system, and wherein the OFDMA
communication system comprises: a wide area wireless OFDMA
communication network.
24. A method for scheduling OFDMA resources allocated to a
transmitter station for a peer-to-peer communication session with a
receiver station, the method comprising: transmitting, from a base
station to recipient stations including the transmitter station, a
metric request message to request first metric measurement
information from the recipient stations, wherein the metric request
message comprises: an indicator that first metric is to be measured
with respect to selected OFDMA resources of an OFDMA frame that the
base station is requesting more information about; and one or more
first metric categories that a station is to report with respect to
the selected OFDMA resources; receiving the metric request message
at the recipient stations including the transmitter station,
measuring, at each of the at the recipient stations, first metric
with respect to some of the selected OFDMA resources, and
transmitting, from each of the recipient stations, a response
message (RM) comprising information regarding first metric
measurement with respect to some of the selected OFDMA resources,
wherein the response message (RM) generated by the transmitter
station comprises a first response message (RM); transmitting, to
the base station, a resource request message (RRM) from the
transmitter station to request allocation of some of the OFDMA
resources for the peer-to-peer communication session with the
receiver station; and processing the response messages (RMs) at the
base station to determine specific ones of the OFDMA resources to
be allocated to the transmitter station.
25. A method for scheduling OFDMA resources allocated to a
transmitter station for a peer-to-peer communication session with a
receiver station, the method comprising: transmitting, from a base
station to recipient stations including the transmitter station, a
request for first metric measurement information to be measured
with respect to selected OFDMA resources of an OFDMA frame;
receiving the request message at the recipient stations; measuring,
at each of the recipient stations, first metric with respect to
some of the selected OFDMA resources, and transmitting, from each
of the recipient stations, a response message (RM) comprising
information regarding first metric measurements with respect to
some of the selected OFDMA resources; and processing the response
messages (RMs) at the base station to determine specific ones of
the OFDMA resources to be allocated to the transmitter station for
the peer-to-peer communication session with the receiver station.
Description
RELATED APPLICATIONS
[0001] The present application is related to the following U.S.
application commonly owned with this application by Motorola, Inc.:
Ser. No. ______, filed Jan. 27, 2009 concurrently with the present
application, titled "Reactive Scheduling Methods and Apparatus to
Enable Peer-to-Peer Communication Links in a Wireless OFDMA System"
(attorney docket no. CM12359), the entire contents of which being
incorporated herein by reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates generally to wireless
communications and more particularly to methods and apparatus for
scheduling resources in Orthogonal Frequency-Division Multiple
Access (OFDMA) communication networks for peer-to-peer
communications among stations operating therein.
BACKGROUND
[0003] Orthogonal Frequency-Division Multiple Access (OFDMA) is a
multiple access method for sharing a radio frequency (RF) channel
among multiple users. OFDMA uses an orthogonal frequency-division
multiplexing (OFDM) digital modulation scheme to modulate
information signals. OFDMA can be described as a combination of
frequency domain and time domain multiple access. In OFDMA, a
communication space is divided into a plurality of time slots, and
each time slot is further divided into a number of frequency
sub-channels each having at least one of its own sub-carriers. In
OFDMA systems, both time and/or frequency resources are used to
separate multiple user signals. Transmissions to/from multiple
users are separated using time slots and sub-channels within each
notwithstanding possibly significant effort and many design choices
motivated by, for example, available time, current technology, and
economic considerations, when guided by the concepts and principles
disclosed herein will be readily capable of generating such
software instructions and programs and ICs with minimal
experimentation.
[0004] The Abstract of the Disclosure is provided to allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features are grouped together in various embodiments for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separately claimed subject matter. time
slot such that users' signals can be separated in the time domain
and/or in the frequency domain. Thus, in OFDMA, resources can be
partitioned in the time-frequency space.
[0005] Recently, broadband wireless networks have been developed
that implement OFDMA. For instance, IEEE 802.16 networks are one
example. As used herein, "IEEE 802.16" refers to a set of IEEE
Wireless LAN (WLAN) standards that govern broadband wireless access
methods. IEEE 802.16 standards have been and are currently being
developed by working group 16 of the IEEE local area
network/metropolitan area network (LAN/MAN) Standards Committee
(IEEE 802). Any of the IEEE standards or specifications referred to
herein may be obtained at
http://standards.ieee.org/getieee802/index.html or by contacting
the IEEE at IEEE, 445 Hoes Lane, PO Box 1331, Piscataway, N.J.
08855-1331, USA. The Institute of Electrical and Electronics
Engineers (IEEE) 802.16 Working Group on Broadband Wireless Access
Standards is a unit of the IEEE 802 LAN/MAN Standards Committee
that aims to prepare formal specifications to support the
development and deployment of broadband Wireless Metropolitan Area
Networks. In such 802.16 communication networks, communications
signals between a base station and a station are modulated using
OFDM. In one configuration, the OFDMA channel is split into a
number of time slots. Each time slot is further divided into a
number of frequency sub-channels (e.g., one 70 MHz wide time slot
can be divided into fourteen sub-channels each being five MHz
wide).
Near-Far Problem
[0006] In a wireless communication system, the near-far problem
refers to the situation where a receiver receives a low-power
signal from a transmitter and a high-power signal from a different
transmitter at the same time, resulting in desensitization or
"desense" of the receiver to the low-power signal. In other words,
the high-power signal may cause the low-power signal to fall below
the receiver's detectability threshold. For instance, when a high
power transmitter is located near a receiver operating in the same
time slot but on a different frequency sub-channel, the high
transmit energy can desensitize the receiver.
Scheduling
[0007] Scheduling algorithms are widely used in wireless networks
for allocating or distributing communication resources (e.g., time
slots and/or sub-channels) among stations to take advantage of
instantaneous channel variations by giving priority to the stations
with favorable channel conditions. For instance, in an OFDMA
communication system, the base station can include a time-division
multiple access (TDMA) scheduler that schedules time/frequency
resources used by each normal uplink communication and each
downlink communication. A normal uplink communication is when a
station transmits to a base station and downlink communication when
the base station transmits to a station. A scheduler may assign an
uplink communication on different sub-channels within the same time
slot to different stations. In particular, the base station
scheduler may schedule these uplink communications either in
different time slots or in the same time slot and uses power
control to prevent/reduce near-far interference among various
stations communicating to the base station in the system. The TDMA
scheduler avoids near-far problems by creating time-orthogonal
uplink and downlink transmissions, and through uplink power
control. For example, in OFDMA solutions which have a base station
centric deployment, such as IEEE 802.16, the near-far problem is
reduced by forcing each base station to create either time (TDD) or
frequency (FDD) orthogonal uplinks and downlinks to prevent
desensitization of the mobile receiver. Power control of uplink
transmissions from a mobile station can be used to assure that
signals arrive at the base station receiver at similar power levels
thereby preventing desensitization of the base station's
receiver.
[0008] Thus, in networks such as these, in which stations
communicate directly with a base station using orthogonal
frequency-division multiple access (OFDMA) for the uplink, such
TDMA scheduling techniques can be used to separate low-power and
high-power users in time to avoid near-far problems. However, as
will be described below, such TDMA scheduling techniques will not
work in all types of OFDMA networks.
BRIEF DESCRIPTION OF THE FIGURES
[0009] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements throughout the
separate views, together with the detailed description below, are
incorporated in and form part of the specification, and serve to
further illustrate embodiments of concepts that include the claimed
invention, and explain various principles and advantages of those
embodiments.
[0010] FIG. 1 illustrates an example of a wireless communication
network for use in one implementation of the present invention;
[0011] FIG. 2 illustrates an example of a base station (BS) in
accordance with some embodiments of the present invention;
[0012] FIG. 3 illustrates an example of a station (STA) in
accordance with some embodiments of the present invention;
[0013] FIG. 4 illustrates resource allocations within a single
OFDMA frame with resources split into uplink resources in an uplink
portion of the frame and downlink resources in a downlink portion
of the frame in accordance with some embodiments;
[0014] FIG. 5 illustrates a resource map information element (RMIE)
that is generated and broadcast by a base station (BS) in
accordance with some embodiments;
[0015] FIG. 6 illustrates a grant metric information element (GMIE)
that is generated and broadcast by a base station (BS) in
accordance with some embodiments;
[0016] FIG. 7 illustrates a resource map response message (RMRM)
that is generated and unicast by a station in accordance with some
embodiments;
[0017] FIG. 8 illustrates a grant metric response message (GMRM)
that is generated and unicast by a destination/receiver station (B)
in accordance with some embodiments;
[0018] FIG. 9 illustrates proactive scheduling method for
scheduling and allocating uplink (UL) resources in accordance with
some embodiments;
[0019] FIG. 10 is flow chart illustrating processing of an RMIE
during a proactive scheduling method in accordance with some
embodiments;
[0020] FIG. 11 is flow chart illustrating processing performed at a
source/transmitter station (Z) during a proactive scheduling method
in accordance with some embodiments;
[0021] FIG. 12 is flow chart illustrating processing performed at a
base station during a proactive scheduling method in accordance
with some embodiments;
[0022] FIG. 13 is flow chart illustrating a method performed at a
base station for updating peer information for a source/transmitter
station (Z) that is requesting the uplink resource grant during a
proactive scheduling method in accordance with some
embodiments;
[0023] FIG. 14 is flow chart illustrating processing performed at a
base station for determining which time slots of the resource
allocation map are to be marked excluded time slots (TS.sub.x) and
preferred time slots (TS.sub.p) during a proactive scheduling
method in accordance with some embodiments;
[0024] FIG. 15 is a flowchart illustrating a reactive scheduling
method in accordance with some embodiments;
[0025] FIG. 16 is a flowchart illustrating processing performed by
a destination/receiver station (B) performs to determine whether to
request a new uplink resource allocation during a reactive
scheduling method in accordance with some embodiments;
[0026] FIG. 17 is flow chart illustrating processing performed at a
base station during a reactive scheduling method in accordance with
some embodiments; and
[0027] FIG. 18 is flow chart illustrating a method performed at a
base station for updating peer information for the
destination/receiver station (B) that is requesting the uplink
resource re-allocation during the reactive scheduling method in
accordance with some embodiments.
[0028] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the present invention.
[0029] The apparatus and method components have been represented
where appropriate by conventional symbols in the drawings, showing
only those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
DETAILED DESCRIPTION
[0030] Although the TDMA scheduling techniques described above,
work well in situations where all stations communicate with and are
assigned or scheduled resources by a central base station, these
techniques do not work in mixed networks that also include direct
station-to-station or "peer-to-peer" communication between
stations. With peer-to-peer communication, there is no concept of
uplink and downlink since communications between the stations are
direct and do not implicate a base station. OFDMA communication
systems allowing peer-to-peer and mesh ad-hoc traffic will
experience significant near-far issues if conventional TDMA
uplink/downlink scheduling is used. As such, with OFDMA
communication systems such as these, it would be desirable to add
capability for scheduled peer-to-peer and mesh hopping
communication links. Accordingly, it would be desirable to provide
new schedulers and scheduling techniques for use in future OFDMA
systems that allow for peer-to-peer communication.
[0031] In one embodiment, systems, methods and apparatus are
provided for scheduling OFDMA resources allocated to a transmitter
station for a peer-to-peer communication session with a receiver
station. The disclosed systems, methods and apparatus can be
implemented in an OFDMA communication system such as a wide area
wireless OFDMA communication network. In such systems and networks,
a base station defines a cell in which a particular wideband
frequency channel is divided into multiple OFDMA time slots or
subframes and in which information that is transmitted is OFDM
modulated. Particular examples of such systems and networks include
a WiMAX IEEE 802.16 compliant network or a 3GPP Long Term Evolution
(LTE) compliant network.
[0032] The base station maintains a resource allocation map. The
resource allocation map includes particular OFDMA resources of an
OFDMA frame that have been allocated to particular stations that
are identified by particular station identification numbers. Each
of the OFDMA resources is a OFDMA frequency sub-channel within an
OFDMA time slot. In accordance with the disclosed systems, methods
and apparatus, the base station can generate a resource map
information element (RMIE) that include a Partial Resource
Allocation Map (PRAM). The PRAM specifies selected OFDMA resources
(of the OFDMA frame) that the base station is requesting more
information about. The PRAM also include an indicator that a first
metric (e.g., one or more Radio Frequency (RF) quality metrics such
as Receive Signal Strength (RSS) power levels, Range,
Signal-to-Noise Ratio (SNR), Signal-to-interference-plus-Noise
Ratio (SINR)) is to be measured with respect to the selected OFDMA
resources. The PRAM also specifies a number of first metric
measurements being requested with respect to the selected OFDMA
resources, and a first metric categories field which identifies one
or more first metric categories a station is to report with respect
to the selected OFDMA resources. The base station broadcasts the
the RMIE to recipient stations including a transmitter station so
that the base station can request first metric measurement
information from the recipient stations based on information it has
specified in the PRAM.
[0033] Upon receiving the RMIE, the recipient stations including
the transmitter station, can measure first metric with respect to
at least some of the selected OFDMA resources specified in the
PRAM, and then each of the recipeint stations can generate and
transmit a resource map response message (RMRM) to the base
station. Each RMRM includes information regarding first metric
measurements made with respect to some of the selected OFDMA
resources that the particular station has measured. Each of the
recipient stations can generate a RMRM by sorting measured first
metric for each of the particular ones of the selected OFDMA
resources into one of a plurality of first metric categories. These
first metric categories categorize the particular ones of the
selected OFDMA resources based on measured first metric, and can
include, for example, a high first metric category that includes
information regarding peer stations that cause high level
interference (e.g., peer stations having higher measured RSS levels
or lower measured SINR levels), and a low first metric category
that cause low level interference (e.g., peer stations having lower
measured RSS levels or high measured SINR levels). Using this
information, a partial resource measurement map (PRMM) is generated
that includes the plurality of first metric categories. Each of the
first metric categories includes first metric measurement
information regarding some of the particular ones of the selected
OFDMA resources. The PRMM generated by each station is included as
part of the RMRM for generated by that particular station. In the
description that follow, the RMRMs and PRMMs generated by the
transmitter station will be referred to as first RMRMs and first
PRMMs to differentiate it from RMRMs and PRMMs generated by other
recipient stations.
[0034] In one implementation, each RMRM includes a resource type
field that specifies a type of resource that the particular station
is reporting in the RMRM, a total categories field that specifies a
total number of different first metric categories being reported in
the RMRM, and a partial resource measurement map (PRMM) comprising:
a plurality of first metric categories each including information
regarding first metric measurements made by the particular station
for selected ones of the selected OFDMA resources specified in the
PRAM. The plurality of first metric categories can include a high
first metric category used to report high power first metric
measurements, a medium first metric category used to report medium
power first metric measurements, and a low first metric category
used to report low power first metric measurements. In addition,
each of the first metric categories comprise a plurality of fields
used to report information regarding first metric measurements by
the particular station for that first metric category The plurality
of fields can include a category identifier field that identifies
the particular first metric category, a number measured field that
specifies a number of first metric measurements that are included
for the particular first metric category, and a category MAP data
field that specifies particular resource locations in the resource
allocation map for the particular first metric category. Again,
each particular resource location is specified as at least one
specific sub-channel and at least one time slot.
[0035] The transmitter station also generates and transmits a
resource request message (RRM) to request allocation of some of the
OFDMA resources for the peer-to-peer communication session with the
receiver station. The resource request message (RRM) can include,
for example, information regarding the station type of the
transmitter station, information regarding the size of the packet
to be transmitted by the transmitter station, and an indicator
which indicates the type of peer-to-peer communication session the
transmitter station would like to set up with the receiver station
including information regarding QoS requirements for that type of
peer-to-peer communication session.
[0036] Upon receiving the first RMRM and the RRM from the
transmitter station, the base station can process the RMRMs to
determine specific ones of the OFDMA resources to be allocated to
the transmitter station for the peer-to-peer communication session
with the receiver station. The specific ones of the OFDMA resources
allocated to the transmitter station each comprise: an allocated
OFDMA sub-channel within a particular OFDMA time slot. The specific
ones of the OFDMA resources are allocated such that other stations
communicating over different OFDMA sub-channels of the particular
OFDMA time slots will not cause near-far problems for the receiver
station, and such that communications by the transmitter station
using the specific ones of the OFDMA resources will not cause
near-far problems for the other receiver stations communicating
over different OFDMA sub-channels of the particular OFDMA time
slots.
[0037] For example, the base station can determine updated peer
station information for the transmitter station based on the one or
more first PRMMs from the first RMRM, and use this peer information
to schedule a first OFDMA resource in a first OFDMA time slot for a
first transmission by the transmitter station to the receiver
station, and to schedule other OFDMA resources in other OFDMA time
slots for other transmissions by high first metric peer stations of
the receiver station (i.e., station having high power first
metric). This way, the first transmission will be received by the
receiver station at a time when the high first metric peer stations
of the receiver station are not transmitting. Accordingly, the
first transmission is isolated in the time domain from the other
transmissions by the high first metric peer stations of the
receiver station.
[0038] To explain further, in accordance with one exemplary
embodiment, the base station can determine updated peer station
information for the transmitter station by extracting information
regarding first metric measurements made by the transmitter station
for the selected ones of the selected OFDMA resources from the
first PRMMs. The base station can then use the resource allocation
map maintained at the base station to translate the selected ones
of the selected OFDMA resources into corresponding peer station
identification numbers. The base station can then determine first
metric categories from the one or more first PRMMs for each of the
peer station indentification numbers, and assign each particular
peer station identification number to one of: a high power first
metric transmitter peer list that specifies peer stations having
high power first metric, a low power first metric transmitter peer
list that specifies peer stations having low power first metric,
and a medium power first metric transmitter peer list that
specifies peer stations having medium power first metric. Using
this information, the base station can create an entry in a peer
memory map (PMM) for the transmitter station. The PMM comprises a
plurality of rows, and a plurality of columns. The plurality of
columns can include a first column that lists peer station
identification numbers corresponding to peer-to-peer enabled
stations that can potentially engage in peer-to-peer communications
including the transmitter station and the receiver station. Each
row corresponds to entry for a particular peer-to-peer enabled
station that is identified in the first column by a particular peer
station identification number. The plurality of columns can also
include a second column comprising the high power first metric
transmitter peer list that specifies peer stations having high
power first metric. The second column lists peer station
identification numbers for peer stations of the corresponding
station in the first column. The plurality of columns can also
include a third column comprising the low power first metric
transmitter peer list that specifies peer stations having low power
first metric. The third column lists peer station identification
numbers for peer stations of the corresponding station in the first
column. The plurality of columns can also include a fourth column
comprising the medium power first metric transmitter peer list that
specifies peer stations having medium power first metric. The
fourth column lists peer station identification numbers for peer
stations of the corresponding station in the first column.
[0039] The base station can then process the first PRMM provided in
the first RMRM and other PRMMs provided in other RMRMs from other
recipient stations to generate a "high impact peer set" and a "low
impact peer set." The high impact peer set identifies stations in
the high power first metric transmitter peer list of the
transmitter station that are susceptible to near-far issues when
one station that belongs to the high impact peer set transmits
while another station that belongs to the high impact peer set is
receiving a different transmission from another station that does
not belong to the high impact peer set. By contrast, the low impact
peer set that identifies stations in the low power first metric
transmitter peer list of the transmitter station that are not
susceptible to near-far issues when one station that belongs to the
low impact peer set transmits while another station that belongs to
the low impact peer set is receiving a different transmission from
another station that does not belong to the low impact peer set.
The base station can then use the information in the resource
allocation map, the high impact peer set and the low impact peer
set to determine preferred OFDMA time slots (TS.sub.p) of the OFDMA
frame and excluded OFDMA time slots (TS.sub.x) of the OFDMA frame,
and can mark the preferred OFDMA time slots (TS.sub.p) and excluded
OFDMA time slots (TS.sub.x) in the resource allocation map that it
maintains. In one implementation, the base station can mark any
time slots allocated to peer stations in a high impact peer set of
the receiver station as excluded OFDMA time slots (TS.sub.x), and
can mark any time slots allocated to peer stations in the high
impact peer set of the transmitter station as preferred OFDMA time
slots (TS.sub.p). When the high impact peer set of the transmitter
station includes no peer stations, the base station can mark any
time slots allocated to peer stations in a low impact peer set of
the receiver station as preferred OFDMA time slots (TS.sub.p). When
an OFDMA time slot is marked as being both an excluded time slot
(TS.sub.x) and preferred time slot (TS.sub.p), the base station can
mark the OFDMA time slot: as a preferred OFDMA time slot (TS.sub.p)
when the transmitter station is a member of the high impact peer
set of the receiver station, or as an excluded OFDMA time slot
(TS.sub.x) of the OFDMA frame when the transmitter station is not a
member of the high impact peer set of the receiver station.
[0040] The base station can then estimate a resource allocation
size (RAS) for the peer-to-peer communication session between the
transmitter station and the receiver station. The base station can
determine based on the estimated RAS, a resource allocation to
allocate for the peer-to-peer communication session between the
transmitter station and the receiver station. This resrouce
allocation includes at least one of the preferred OFDMA time slots
(TS.sub.p) and at least one sub-channel in that preferred OFDMA
time slot (TS.sub.p). However, in general, the "resource
allocation" can be any combination of one or more preferred time
slots (TS.sub.p) and any combination of one or more
subcarriers/sub-channels within the one or more preferred time
slots (TS.sub.p). The base station can then transmit a resource
grant message (RGM) to notify the transmitter station and the
receiver station of the resource allocation to the transmitter
station and the receiver station for the peer-to-peer communication
session between them.
[0041] As the peer-to-peer communication session between the
transmitter station and the receiver station takes place the
resource measurement information specified in the RMIE can be
dynamically adjusted as traffic characteristics change within the
OFDMA cell defined by the base station.
[0042] Embodiments of the present invention can apply to a number
of network configurations. Prior to describing some embodiments,
one example of a network configuration in which these embodiments
can be applied will now be described with reference to FIG. 1.
[0043] Embodiments of the present invention can apply to a number
of network configurations. Prior to describing some embodiments,
one example of a network configuration in which these embodiments
can be applied will now be described with reference to FIG. 1.
[0044] FIG. 1 illustrates a wireless communication network 100 for
use in an implementation of the present invention. The network 100
is capable of operating in compliance with the IEEE 802.16
standards. As illustrated, the network 100 includes a plurality of
subscriber stations 110-n and at least one base station 105. As
used herein, the term "uplink (UL)" refers to a communication link
for carrying information from a station to a base station (or
alternatively clusterhead station or access point), and can also
refer to a transmission from a station to a base station. As used
herein, the term "downlink (DL)" refers a communication link that
carries information from a base station (or alternatively
clusterhead station or access point) to a station and can also
refer to a transmission from a base station to a station. In the
embodiments described herein, both the UL and DL are transmitted
using OFDMA techniques that will be described in greater detail
below.
[0045] The stations 110 are wireless communication devices enabled
to communicate "peer-to-peer" or directly with another station, and
to communicate with the base station 105 over OFDMA communication
links. A station is potentially mobile (i.e., not fixed) and can be
mobile at any particular time, whereas the base station 105 is
fixed at a particular location.
[0046] The base station 105 can communicate data and/or control
signaling information with plurality of stations 110-n. In FIG. 1,
the single-ended, dotted line arrows represent a downlink that
carries control or signaling information transmitted from the base
station 105, and the double-ended, solid line arrows represent an
uplink that carries data and/or control information transmitted
from a station to the base station 105 and a downlink that carries
data information and/or control or signaling information
transmitted from the base station 105 to a station. The
double-ended, dotted-line arrows represent a peer-to-peer
communication link that carries information from a station to
another station. In network 100, stations SS1 110-1 and SS5 110-5
have direct peer-to-peer communication links with stations 110-3
and 110-2, respectively.
[0047] To provide greater control over the network many decisions
are made at the base station 105. For example, centralized
scheduling algorithms can be implemented within the base station
105, and the base station 105 can be responsible for making
resource scheduling decisions for allocating resources to the
various stations (SSs) 110-n operating within the cell that is
defined by the base station (e.g., in the base station's "cell").
As will be described below, the base station 105 is responsible for
making scheduling decisions. As noted above, in an OFDMA system,
the uplink and downlink radio frequency resources are divided into
multiple slots in the time domain, and into a number of subcarriers
in the frequency domain. Within one time slot, different
subcarriers can be allocated to different users in any order.
Moreover, the subcarriers assigned to a particular user can vary
from time slot to time slot (e.g., a diversity subcarrier
sub-channelization scheme where subcarriers assignments do not need
to follow the precise pattern in each time slot). As used herein,
the term "resource" refers to a time slot within an OFDMA frame 400
and a frequency subcarrier/sub-channel within that time slot. In
some systems, two or more resources are grouped together in a
"tile" that includes more than one resource (e.g., one time slot
with two or more subcarriers/sub-channels in that time slot grouped
together or two or more time slots and one or more
subcarriers/sub-channels in each time slot grouped together). The
term "resource allocation" refers to resources allocated (or
granted) to a particular source/transmitter station by a base
station for communications between the source/transmitter station
and a destination/receiver station. A resource allocation may
comprise any combination of (1) time slots and (2) any combination
of subcarriers/sub-channels within those time slots that are
allocated by a base station to a transmitting/source station. The
minimum resource allocation is one time slot and one
subcarrier/sub-channel within that time slot. In some
implementations, resources are allocated in a rectangular
aggregation of contiguous frequency sub-channels and time
slots.
[0048] In accordance with the various embodiments described herein,
the base station 105 schedules uplink resources and downlink
resources for communication with various stations 110-n. In
addition, as will be described below, the base station 105 also
schedules resources for direct, peer-to-peer communication links
that are used to communicate between stations. Prior to describing
the scheduling methods in detail below, one example of a base
station 205 and one example of a station 310 will now be described
with reference to FIGS. 2 and 3, respectively.
[0049] FIG. 2 illustrates an example of a base station 205 in
accordance with some embodiments of the present invention. As
illustrated, the base station 205 comprises a plurality of ports
250-n, a controller 253, and a memory 262.
[0050] Each port 250-n provides an endpoint or "channel" for
network communications by the base station 205. Each port 250-n may
be designated for use as, for example, an IEEE 802.16 port or a
backhaul port. For example, the base station 205 can communicate
with one or more stations within an 802.16 network using an IEEE
802.16 port. An IEEE 802.16 port, for example, can be used to
transmit and receive both data and control, signaling or management
information. A backhaul port similarly can provide an endpoint or
channel for backhaul communications by the base station 205. For
example, the base station 205 can communicate with a wired backhaul
via the backhaul port; the backhaul port does not need to
communicate using OFDMA or OFDM.
[0051] Each of the ports 250-n are coupled to the controller 253
for operation of the base station 205. Each of the ports employs
conventional OFDM demodulation and modulation techniques for
receiving and transmitting communication signals respectively, such
as packetized signals, to and from the base station 205 under the
control of the controller 253. The packetized signals can include,
for example, voice, data or multimedia information, and control
information. As used herein, the term "data" can refer to, for
example, data generated by applications, a network management
entity, or any other higher-layer protocol entities that may use
the IEEE 802.16 Media Access Control (MAC) layer to transfer
information. Examples of user data include, for example, packets
generated by voice, video, e-mail, file transfer applications and
network management agents. As used herein, the term "control
information" can refer to, for example, messages and signaling used
by the IEEE 802.16 MAC layer and physical (PHY) layer to carry out
its own protocol functionality. Control information includes
periodic control information and aperiodic control information. As
used herein, the term "periodic control information" can refer to,
for example, preambles, midambles, synchronization sequences,
timing and frequency correction channels or any other signaling
used to ensure correct reception of the messages transmitted in a
frame. Examples of periodic control information include, for
example, frame control information such as a frame control header
(FCH), a synchronization channel, preamble information, information
regarding the frame structure, markers which flag the start of the
frame, a downlink MAP (DL-MAP) message and other types of control
information. As used herein, the term "aperiodic control
information" can refer to, for example, messages transmitted
aperiodically to ensure proper protocol behavior and station
upkeep. Examples of aperiodic control information include, for
example, management and control information, such as capability
announcements, ranging messages, measurement reports, and handoff
instructions.
[0052] Among other modules (not illustrated), the controller 253
includes a scheduler module 259 that includes a proactive scheduler
module 255 and a reactive scheduler module 257. The scheduler
module 259 and the parameters utilized therein can be hard coded or
programmed into the base station 205 during manufacturing, and/or
can be programmed over-the-air upon customer subscription, and/or
can be a downloadable application. Other programming methods can be
utilized for programming the scheduler module 259 into the base
station 205. In one implementation, the scheduler module 259 can be
implemented within the controller 253 as illustrated, or
alternatively can be an individual preprocessing module
communicatively coupled to the controller 253 (not shown).
[0053] To perform the necessary functions of the base station 205,
the controller 253 is coupled to the memory 262, which preferably
includes a random access memory, a read-only memory (ROM), an
electrically erasable programmable read-only memory (EEPROM), and
flash memory. The memory 262 can be integrated within the base
station 205, or alternatively, can be at least partially contained
within an external memory such as a memory storage device. The
memory storage device, for example, can be a subscriber
identification module (SIM) card.
[0054] FIG. 3 illustrates a station 310 in accordance with some
embodiments of the present invention. As illustrated, the station
310 comprises a plurality of ports 368-n. Each port 368-n may be
designated for use as, for example, an IEEE 802.16 port. For
example, the plurality of ports 368-n can include an IEEE 802.16
port, which is used to communicate with a base station and/or one
or more other stations. An IEEE 802.16 port, for example, provides
an endpoint or "channel" for 802.16 network communications by the
station 310 with base station 205, and can be used to transmit and
receive both data and control/signaling/management information.
[0055] The station 310 further comprises a controller 371 and a
memory 383. Each of the ports 368-n are coupled to the controller
371 for operation of the station 310. Each of the ports employs
conventional demodulation and modulation techniques for receiving
and transmitting communication signals to and from the station 310,
respectively, under the control of the controller 371. The
packetized signals include those described above.
[0056] The controller 371 includes a local scheduler module 380
that includes a proactive sceduler module 355 and a reactive
scheduler module 357. The local scheduler 380 and the parameters
utilized therein can be hard coded or programmed into the station
310 during manufacturing, can be programmed over-the-air upon
customer subscription, or can be a downloadable application. Other
programming methods can be utilized for programming the local
scheduler 380 into the relay station 310. The local scheduler 380
can be contained within the controller 371 as illustrated, or
alternatively can be individual modules operatively coupled to the
controller 371 (not shown). The operation of each of these modules
will be described herein.
[0057] To perform the necessary functions of the station 310, the
controller 371 and the local scheduler 380 are each coupled to the
memory 383, which preferably includes a random access memory, a
read-only memory (ROM), an electrically erasable programmable
read-only memory (EEPROM), and flash memory. The memory 383 can be
integrated within the station 310, or alternatively, can be at
least partially contained within an external memory such as a
memory storage device. The memory storage device, for example, can
be a subscriber identification module (SIM) card. A SIM card is an
electronic device typically including a microprocessor unit and a
memory suitable for encapsulating within a small flexible plastic
card. The SIM card additionally includes an interface for
communicating with the station 310.
[0058] Embodiments that will be described below relate to
scheduling communication resources. An example of resources
scheduled by a base station will now be described with reference to
FIG. 4.
[0059] FIG. 4 illustrates resource allocations within a single
OFDMA frame 400. In the OFDMA frame 400 resources are split into
uplink resources in an uplink portion 450 of the frame 400 and
downlink resources in a downlink portion 410 of the frame 400 for a
TDD embodiment. Individual resource allocations within the frame
400 are shown as shaded rectangles. In other words, the shaded
rectangles are resources that have been allocated to particular
stations. These allocated resources are also maintained by the base
station in a list called a resource allocation map. The downlink
and uplink portions 410, 450 are groups of time slots that can also
be called, for example, uplink and downlink sub-frames or zones.
Typically, the size in time of the frame 400 is fixed whereas the
partition between downlink and uplink portions 410, 450 can be
adjusted. The partition between downlink and uplink portions 410,
450 of the frame 400 and resource allocations of the frame 400 are
maintained in a resource allocation map located in the base station
memory in accordance with some embodiments. The resource allocation
map includes entries for all downlink (DL) resources and all uplink
(UL) resources of the base station, and also specifies which ones
of the DL and UL resources are currently/presently allocated and to
which stations those resources are currently/presently allocated
(if at all).
[0060] In this embodiment, time division duplexing (TDD) is
implemented such that the uplink and downlink are allocated
different (non-overlapping) time-periods of the frame. As noted
above, OFDM modulation is implemented for downlink (DL) and uplink
(UL) communications, and a particular frequency band is divided
into multiple OFDMA time slots. Each time slot has a number of
subcarriers/sub-channels of a wideband channel. In the resource
allocation map, the time slots correspond to the vertical columns
412-428 and 452-468 of the frame 400, where the group of time slots
define an OFDMA frame 400. The subcarriers/sub-channels 432-446
correspond to horizontal rows of the frame 400, where the same
subcarriers/sub-channels are used for both uplink and downlink.
[0061] Although not illustrated, the resource allocation map could
also include specific dedicated "zones." These dedicated zones are
portions of the frame 400 that are reserved exclusively for or
dedicated to direct station-to-station (i.e., "ad hoc" or
"peer-to-peer") communication links, or alternatively, for direct
station-to-relay station communication links. Thus, in one
embodiment, direct station-to-station communication links can be
interspersed with normal station-to-BS uplinks. In another
embodiment, a subset or region or zone of time slots in the uplink
(UL) portion/zone 450 of the frame 400 can be dedicated or devoted
exclusively to direct station-to-station communication links. In
this exclusive region, no station-to-BS traffic is allowed or
scheduled.
[0062] In one embodiment, the base station implements a front-back
scheduler module. DL resource allocations are allocated in a
downlink (DL) portion/zone 410 of the frame 400 (i.e., time slots
at the front of the frame 400), and UL resource allocations are
allocated in an uplink (UL) portion/zone 450 of the frame 400
(i.e., time slots at the rear of the frame 400). As such, the
resource allocation map includes a downlink (DL) portion/zone 410
of downlink resources that are to be allocated for downlink
communications and an uplink (UL) portion/zone 450 of uplink
resources that are to be allocated for uplink communications.
[0063] Each shaded-rectangle in FIG. 4 represents a frequency
subcarrier/sub-channel and time slot allocation to a particular
station for a particular communication link (either with the base
station or with another station). In this example, it is assumed
that a diversity subcarrier/sub-channelization scheme is
implemented such that different subcarriers/sub-channels within one
time slot can be allocated to different stations in any order.
Moreover, the subcarriers/sub-channels assigned to a particular
station can vary from time slot to time slot (i.e., subcarriers
assignments do not need to follow the same pattern in each time
slot). FIG. 4 will be referenced and described in greater detail
below.
[0064] In the description that follows, it is assumed that
resources for direct station-to-station (i.e., "ad hoc" or
"peer-to-peer") communication links are allocated from uplink
resources in the uplink (UL) portion/zone 450 of the OFDMA frame
400. It will be appreciated by those of ordinary skill in the art
that, in other embodiments, resources for direct station-to-station
(i.e., "ad hoc" or "peer-to-peer") communication links can be
allocated from downlink resources in the downlink (DL) portion/zone
410 of the OFDMA frame 400.
[0065] Information Elements and Response Messages
[0066] To enable scheduling of uplink resources for peer-to-peer or
station-to-station communication links, embodiments disclosed
herein define new broadcast information elements (IEs) and unicast
response messages (RMs) that are used in conjuction with the
various embodiments described below. Prior to describing various
embodiments, various information elements (IEs) that can be used in
conjunction with these embodiments will now be described in detail.
The new information elements include a resource map information
element (RMIE) and a grant metric information element (GMIE) that
will be described with respect to FIGS. 5 and 6, respectively. In
one non-limiting implementation, the RMIE and GMIE are transported
over-the-air (OTA) from a base station using a beacon signal;
however, it will be appreciated by those skilled in the art that
the RMIE and GMIE can be transported using a wide variety of other
mechanisms or messages. Other potential information sources that
could be used to carry information included in the RMIE and GMIE
include routing messages, active and passive probe messages, hello
messages and channel estimation measurements.
[0067] In addition, the new response message include a resource map
response message (RMRM) and a grant metric response message (GMRM)
that will be described below with regard to FIGS. 7 and 8,
respectively. The RMRM and GMRM are unicast over the air from
particular stations to a base station. As will be described below,
the RMIE (FIG. 5) and RMRM (FIG. 7) are exchanged in a proactive
scheduling method and the GMIE (FIG. 6) and GMRM (FIG. 8) are
exchanged in a reactive scheduling method.
[0068] FIG. 5 illustrates a resource map information element (RMIE)
500 that is generated and broadcast by a base station (BS) in
accordance with some embodiments. In some implementations, the base
station can periodically broadcast the RMIE. When implemented in a
WiMax-type system, the RMIE can be placed in the control portion of
each frame so that WiMax-enabled stations can decode these control
messages each time a frame is received. In some implementations,
the RMIE 500 can be located near the beginning of a frame so
stations have adequate time to decode the RMIE 500. The RMIE 500
implicitly indicates that peer-to-peer traffic is allowed by the
base station due to the fact that the RMIE 500 is transmitted. The
RMIE 500 describes information that is used to request partial
resource allocation maps (PRAMs) from stations desiring new
resource grants. A PRAM is communicated from a base station so that
a station knows which resources in a resource allocation map to
monitor so that the station does not have to monitor the entire set
of resources. Resources specified in a PRAM can be presently free
or presently allocated. In other words, each PRAM 530 specifies
resources that the base station wants more information about; a
station can select at least some of these resources in the PRAM (or
all of the resources in the PRAM) to monitor, monitor this selected
subset of resources, make measurements with regard to these
resources, and then report the measurements back to the base
station in an RMRM (FIG. 7). In the description that follows, one
example will be described in which a particular Radio Frequency
(RF) quality metric, namely Receive Signal Strength (RSS) power
levels, is used to describe measurements made by stations. However,
in other embodiments equivalent metrics (or combinations of
equivalent metrics) can be used in conjunction with the methods
described below. Examples of these equivalent metrics can include,
but are not limited to, Signal-to-Noise Ratio (SNR),
Signal-to-interference-plus-Noise Ratio (SINR) and range. For
example, in one implementation, receive signal strength (RSS)
and/or SINR measurements can be requested by the base station in an
RMIE 500. In one specific implementation, that is described below,
the base station uses the RMIE 500 to request information from the
stations that categorizes receive signal strength (RSS) power
levels received for a portion of the resource map. Alternatively,
other radio frequency (RF) quality metrics can be measured with
respect to the selected OFDMA resources. Range can be used in
addition to RSS, SNR or SINR. Range can be measured by looking at
timing differences between packet timestamps made by a transmitter
and receive times (assuming the transmitter and the receiver can
synchronize to a common signal), then multiplying those changes by
the speed of light (c) to get range. Range can also be obtained via
Global Positioning System (GPS) measurements at stations that have
GPS capability. The base station changes the content of the RMIE
500 either periodically or dynamically based on changes in traffic
load and/or traffic type.
[0069] The RMIE 500 includes an information element identification
number (IE ID#) field 510 that is a a unique identification number
for the RMIE 500, an information element size (IE size) field 520
that is used to specify the size (in bytes) of the RMIE 500, a time
slot start field 535 that specifies the starting location of the
PRAM 530 within the resource allocation map, a number of time slots
field 540 that specifies the number of time slots over which a
station is to take RSS measurements (the PRAM 530 does not specify
sub-channels), a resource type (Resource Type) field 550 that is
used to specify a type of resource for which a station is to report
RSS measurements in its RMRM (FIG. 7), a maximum number of reports
(Max # Reports) field 560 that is used to specify a maximum number
of measurements to include in the station's RMRM (FIG. 7), and a
RSS Power Categories field 570 in which each bit identifies whether
or not a particular RF quality metric category should be included
in the station's RMRM (FIG. 7). In one implementation, the resource
type field 560 can include both resource and measurement type. In
this manner, for instance, the base station can request SINR
measurements over a time slot, or SINR measurements over both time
slots and frequency sub-channels, or RSS measurements over a time
slot, or RSS measurements over both time slots and frequency
sub-channels. Additional details regarding one implementation of
the fields of the RMIE 500 are provided below in Table 1.
TABLE-US-00001 TABLE 1 Field Size Description IE ID # 1 byte
Specifies unique identification number for Resource Map IE IE Size
1 byte Specifies size in bytes of the IE Time slot 1 byte Specifies
starting location of PRAM within Start resource allocation map; can
be set to zero to indicate that base station is letting station
decide which time slots to scan # Time 4 bits Specifies a number of
time slots to indicate how slots wide the PRAM is over which a
station can take RSS measurements 0000: No measurements 0001: 2
time slots 0010: 4 time slots . . . 1111: All time slots Resource 2
bits Specifies type of resource that a station reports Type in
response message: 00: RSS for Timeslots only 01: RSS for Timeslot
& Frequency 10: RSS for Grants (Blocks of Time & Frequency)
Max # 5 bits Specifies maximum number of partial resource Reports
allocation map measurements to include in the station response
message RF 3 bits Each bit identifies whether or not a particular
Quality RF quality metric category should be included Metric in the
station response message: Category xx1: Include High Category RSS
measurements x1x: Include Medium Category RSS measurements 1xx:
Include Low Category RSS measurements
[0070] Thus, upon receiving the RMIE, a station measures RSS
information described by the RMIE 500 for selected ones of the time
slots specified in the RMIE 500, sorts its RSS measurements into
groups or categories (e.g., high RSS, medium RSS, low RSS, etc.),
and then reports this information in a RMRM that is described below
with reference to FIG. 7.
[0071] FIG. 6 illustrates a grant metric information element (GMIE)
600 that is generated and broadcast by a base station (BS) in
accordance with some embodiments. In one implementation, the GMIE
600 can be broadcast by the base station in a beacon message. The
GMIE 600 is used to inform destination/receiver stations of
measurements that must be provided when requesting a change in
their current resource allocation. The information requested covers
the time slots for the current grant. The requested information is
eventually used by the base station to improve peer groupings and
to assess whether a resource re-allocation is warranted. As noted
above, the GMIE 600 is only "used" during a reactive scheduling
method for "reallocating" resources that are granted to a
particular station. Although the GMIE 600 is broadcast and received
by all stations (within communication range), the GMIE 600 is only
processed by destination/ receiver stations involved in an active
communication session since only those stations can collect QoS
metrics requested by the base station via the GMIE 600.
[0072] The GMIE 600 includes an information element identification
number (IE ID#) field 610 that is a unique identification number
for the GMIE 600, an information element size field 620 that is
used to specify the size (in bytes) of the GMIE 600, a measurement
type (Meas. Type) field 630 that is used to specify to the station
a type of QoS measurement that is to be reported by the station in
the GMRM (FIG. 8), a measurement quality field 640 that is used to
specify to the station how many frames 400 to average for each
measurement provided, and in some implementations, can be used to
specify algorithms for combining measurements. In this specific
embodiment, the QoS metrics 630 specified include frame error rate
(FER), SINR, and Analog-to-Digital Converter desense. However, in
other embodiments, additional QoS metrics can be specified. For
example, in an alternative embodiment, the GMIE can specify QoS
metrics regarding the amount of peer-to-peer traffic, the rate the
traffic mix changes, cell load, etc. Additional details regarding
one implementation of the fields 610-640 of the GMIE 600 are
provided below in Table 2.
TABLE-US-00002 TABLE 2 Field Size Description IE ID # 1 byte
Specifies a unique identification number for the Grant Metric IE IE
Size 1 byte Specifies size in bytes of the IE Meas. 3 bits
Specifies type of Measurement Type 000 No measurements xx1 Include
FER x1x Include SINR 1xx Include ADC Desense Meas. 4 bits
Measurement quality tells the station how many Quality frames to
average for each measurement provided. Algorithms for combining
measurements could also be specified.
[0073] Thus, any station that is in a communication session and
would potentially require/desire a new resource allocation, upon
receiving the GMIE 600, measures QoS metrics described by the GMIE
600 for each time slot that it has been allocated. For example, if
a receive station is receiving in time slots 3 and 4, then it would
measure QoS metrics during the communication session on time slots
3 and 4. The station then reports these QoS metrics in a GMRM that
is described below with reference to FIG. 8.
[0074] As will be described below, as traffic changes from base
station-to-station to peer-to-peer, the base station can adjust the
RMIE 500 and/or GMIE 600 to adjust the amount of information
collected by the stations and sent to the base station for creation
of the peer sets needed to prevent near-far scheduling issues. The
base station also adjusts the RMIE 500 and the GMIE 600 to request
an increase or decrease in destination/receiver station (B)
measurements based on the base station perception of how error free
the communication session is. For low loading and/or little
peer-to-peer traffic, little additional uplink resource information
is needed. Only a small amount of uplink RSS resource information
and QoS metrics are required from destination/receiver stations
(B). If this is insufficient for the base station to figure out
what is happening, it can put in a temporary request for additional
information from a specific destination/receiver station (B). In
one implementation, a base station can have a particular station
that it has trouble scheduling. The base station can unicast an
RMIE to this station that requires different measurements than the
standard broadcast RMIE. For example, for high loading and/or high
peer-to-peer traffic the RMIEs and GMIEs can request more
destination/receiver station (B) information. For example, in a
large room (trade show, conference hotel), more information
regarding uplink resources can be requested from a given localized
area. The base station may also use the RMIE or GMIE as a unicast
probe request to a specific destination/receiver station (B) to ask
for more detailed uplink resource information than is required by
the regular RMIE and GMIE. A probe to one destination/receiver
station (B) requesting a full local map can greatly resolve peer
grouping issues in some situations. Using unicast requests for
additional information via the RMIE and GMIE can provide the
information needed by a base station to improve peer group sets
(described below) without significant network overhead.
[0075] FIG. 7 illustrates a resource map response message (RMRM)
700 that is generated and unicast by a station in accordance with
some embodiments. The RMRM 700 from the station is designed to
reduce network traffic. When requesting resources, the station will
send the requested partial resource allocation map information
along with a grant request. In some embodiments the RMRM 700 may be
sent to the base station periodically. One implementation of the
RMRM 700 sent by stations will now be described below.
[0076] The RMRM 700 includes response message identification number
(RM ID#) field 710 that is a unique identification number for this
RMRM 700, a response message size field 720 that is used to specify
the size in bytes of the RMRM 700, and a resource type (Resource
Type) field 730 that is used to specify a type of resource that
this station is reporting in the RMRM 700, and a total categories
(Total Categories) field 735 to specify the total number of
different RF quality metric categories reported in RMRM 700. The
type of resource was previously included in the RMIE 500, but it is
included again in the RMRM 700 since a base station has the option
of changing the default resource type at any time, and therefore
needs to know what type of resource measurement is being specified
in the RMRM 700. As in the description above and in the description
that follows, one example will be described in which a particular
RF quality metric, namely RSS, is used to describe measurements
made by and reported stations. However, in other embodiments
equivalent metrics (or combinations of equivalent metrics) can be
used in conjunction with the methods described below. Examples of
these equivalent metrics can include, but are not limited to,
range, SNR and SINR. For example, in one implementation, RSS and/or
SINR measurements can be reported to the base station in the RMRM
700. In one implementation, the resource type field 730 can include
both resource and measurement type. In this manner, for instance,
the base station can request SINR measurements over a time slot, or
SINR measurements over both time slots and frequency sub-channels,
or RSS measurements over a time slot, or RSS measurements over both
time slots and frequency sub-channels.
[0077] The RMRM 700 also includes a partial resource measurement
map (PRMM) 740 that includes information regarding RSS measurements
made by a particular station for selected ones of the resources
specified in the PRAM 530 specified in the RMIE 500 of FIG. 5. The
PRMM 740 is used to report the measurements requested and specified
in the RMIE 500, and the category MAP data fields 748, 758, 768 are
used to specify the specific sub-channels and time slots. For
example, in the PRMM 740 illustrated in FIG. 7 includes four fields
742, 744, 746, 748 that are used by the station to report RSS
measurements for RSS power category 1, and although not explicitly
illustrated in FIG. 7, can also include four additional fields
752-758 (not illustrated) for RSS power category 2 that are similar
to those for category 1, and four fields 762-768 (not illustrated)
for RSS power category 3 that are also similar to those for
category 1. In this implementation, the three RSS power categories
correspond to high power RSS measurements (category 1), medium
power RSS measurements (category 2), and low power RSS measurements
(category 3). In an alternative embodiment of this invention, fewer
or more RSS power categories can be present. Thus, the PRMM 740
following the total categories field 735 can specify a number of
RSS power category fields (three in the example above). For each
RSS power category reported by the station, there are four fields
that are used to define and provide information for that particular
RSS power category. For instance, in implementations where there
are three RSS power categories, the total categories field 735 will
be set to 3 and there will be a total of tweleve fields--four
fields 742-748 for category 1, four fields 752-758 for category 2,
and four fields 762-768 for category 3.
[0078] In the example illustrated in FIG. 7, the category 1 RSS
power category field 742 identifies the RSS power measurement
category that applies for: a number measured (Category 1 # Meas.)
field 744, and a valid (Category 1 Valid) field 746 and a map data
(Category 1 Map Data) field 748. In this implementation, the
category 1 RSS power category field 742 can be a 3 bit variable
that can be set to 0 to indicate high RSS. The number measured
(Category 1 # Meas.) field 744 can be a 4 bit variable that
specifies a number of high RSS measurements that are included for
the Category 1 RSS measurements. The valid (Category 1 Valid) field
746 indicates whether or not each of the category 1 RSS
measurements contained a valid preamble (i.e., whether the receiver
was also able to decode the preamble, and if so that the measured
RSS signal is valid for the system of interest opposed to being
wireless interference from some other competing system). Valid
field 746 can be used when making decisions about resource
availability in unlicensed spectrum where competing wireless
signals are likely to occur in the operating frequency bands. The
valid filed 746 is not needed in some implementations such as those
operating in licensed WIMAX spectrum. When the valid field 476 is
implemented, the station uses 1 bit per RSS measurement to provide
the information in the valid (Category 1 Valid) field 746. The map
data (Category 1 Map Data) field 748 specifies the map information
requested from and reported to the base station and includes
resource allocation map locations (time slot, frequency
sub-channel) for the category 1 RSS measurements. In one
implementation, the field 748 "Category 1 Map Data" specifies a
tile that defines a time slot and one or more sub-channel frequency
for each measurement. Although the map data (Category 1 Map Data)
field 748 is illustrated using a single row for purposes of
simplicity, it is to be appreciated that the map data (Category 1
Map Data) field 748 can include multiple entries or rows, where
each entry or row specifies specific measurement data for a
particular resource (i.e., particular time slot and a particular
frequency sub-channel). In other words, the map data (Category 1
Map Data) field 748 can include one entry for each resource (i.e.,
particular time slot and a particular frequency sub-channel) that
was measured and is categorized in category 1. In an alternative
embodiment, each entry can include a two-dimensional resource
region (or tile) of the form [Ts1, Ts1, Ts2, Fs2 . . . ]. For
example, the entry [Ts1, Ts1, Ts2, Fs2] would describe a region of
time slots Ts1 to Ts2 and frequency subchannels Ts1 to Fs2, where
all RSS measurements over those resources are specified within the
RF quality metric category field 742. Additional details regarding
one implementation of the fields of the RMRM 700 are provided below
in Table 3.
TABLE-US-00003 TABLE 3 Field Size Description RM ID # 1 byte
Specifies a unique identification number for this RM RM Size 1 byte
Specifies size in bytes of the RM Resource 2 bits Specifies type of
resource that a station reports Type in response message: 00:
Timeslots only 01: Timeslot & Frequency 10: Grants (Blocks of
Time & Frequency) Total 3 bits Identifies the total number of
RSS power Categories categories in the remainder of the table. Each
category will contain 4 fields. Category 1 3 bits Identifies which
RSS power measurement RSS Power category applies for the following
3 fields (# Category Meas, Valid, Map Data). 001: High Power RSS
measurements 010: Medium Power RSS measurements 100: Low Power RSS
measurements Category 1 4 bits Specifies a number of resource map #
Meas. measurements included for the Category 1 RSS measurements.
Category 1 1 bit/meas Indicates whether or not each of the category
1 Valid RSS measurements contained a valid preamble. Category 1
6-10 bits/meas Specifies resource map locations (time slot,
frequency) Map Data for the category 1 RSS measurements . . . . . .
. . .
[0079] A few examples of the content of the PRMM 740 will now be
described to provide context.
[0080] For instance, when the base station had requested, via the
RMIE 500, measurements over the region of time slots 15-20 of the
resource allocation map, an example of the category 1 RF quality
metric category could be as follows:
[0081] Category 1 RSS Power Category=[0] (to indicate high
RSS);
[0082] Category 1 # RSS Measurements=[3];
[0083] Category 1 Valid system for measurement 1=[1];
[0084] Category 1 Valid system for measurement 2=[1];
[0085] Category 1 Valid system for measurement 3=[0] (to indicate
that the receiver could not decode this signal so there may be
external interference or really bad channel conditions);
[0086] Category 1 Map Data for measurement 1=[sub-channel=3], [time
slot=16];
[0087] Category 1 Map Data for measurement 2=[sub-channel=5], [time
slot=18]; and
[0088] Category 1 Map Data for measurement 3=[sub-channel=7], [time
slot=19].
[0089] By contrast, when the base station requests measurements
over the resource region that includes sub-channels 3-10 and time
slots 15-20, the PRMM 740 can include:
[0090] Category 1 RSS Power=[0] (to indicate high RSS);
[0091] Category 1 # RSS Measurement=[3];
[0092] Category 1 Valid system for measurement 1=[1];
[0093] Category 1 Valid system for measurement 2=[1];
[0094] Category 1 Valid system for measurement 3=[0] (to indicate
that the receiver could not decode this signal so there may be
external interference or really bad channel conditions);
[0095] Category 1 Map Data for measurement 1=[sub-channel=3], [time
slot=4];
[0096] Category 1 Map Data for measurement 2=[sub-channel=5], [time
slot=10]; and
[0097] Category 1 Map Data for measurement 3=[sub-channel=7], [time
slot=14].
[0098] In addition, a particular implementation of a station can
specify one, two or three sets of category map data 748, 758, 768.
For instance, if the station also reports three low RSS
measurements then it has to include a set of Category 2
measurements analogous to those above.
[0099] As noted above, a station can measure RSS information
described by the RMIE 500 for selected ones of the time slots
specified in the RMIE 500, and sort its RSS measurements into
groups or categories (e.g., high RSS, medium RSS, low RSS,
etc.).
[0100] In one implementation, category 2 can be used to specify a
group of low RSS measurements. For instance, a station can also
report three low RSS measurements as a set of Category 2
measurements as follows:
[0101] Category 2 RSS Power Category=[1] (to indicate low RSS);
[0102] Category 2 # RSS Meas=[3];
[0103] Category 2 Valid system for measurement 1=[0] This low power
signal was invalid;
[0104] Category 2 Valid system for measurement 2=[1];
[0105] Category 2 Valid system for measurement 3=[1];
[0106] Category 2 Map Data for measurement 1=[sub-channel=4], [time
slot=17], [sub-channel=6], [time slot=17] (These form rectangles in
the resource allocation map);
[0107] Category 2 Map Data for measurement 2=[sub-channel=6], [time
slot=19], [sub-channel=6], [time slot=20]; and
[0108] Category 2 Map Data for measurement 3=[sub-channel=12],
[time slot=18], [sub-channel=14], [time slot=20].
[0109] Notably, in the set of Category 2 measurements, the
"Category_2 RSS Power Category" is set to a different value (1) to
indicate that this measurement is for a low RSS power category.
[0110] FIG. 8 illustrates a grant metric response message (GMRM)
800 that is generated and unicast by a destination/receiver station
(B) in accordance with some embodiments. A GMRM 800 is sent from a
destination/receiver station (B) to a base station to report QoS
metrics measured by the destination/receiver station (B) during a
communication session or call. One implementation of the GMRM 800
sent by destination/receiver stations (B) will now be described
below.
[0111] The GMRM 800 includes response message identification number
(RM ID#) field 810 that is a unique identification number for this
GMRM 800, an response message (RM) size field 820 that is used to
specify the size in bytes of the GMRM 800, and a total categories
field 830 indicating the number of measurement categories included
in the remainder of the table.
[0112] In FIG. 8, two fields 842, 844, are illustrated for
reporting a first QoS category measurement. In particular, the
category measurement type field 842 identifies which QoS
measurement category applies for a category 1 measurement (Category
1 Meas.) field 844 that specifies the station measurement. For
instance, the category measurement type field 842 can indicate a
frame-error-rate (FER) and the category 1 measurement (Category 1
Meas.) field 844 can include a value representing the number of
frame errors measured. However, in some implementations, a
destination/receiver station (B) can report additional QoS metrics
such as Signal-to-interference-plus-Noise Ratio (SINR) and
analog-to-digital converter (ADC) desense. In such implementations,
there can be additional fields for speciflying these additional QoS
metrics. For instance, in an implementation, where the
destination/receiver station (B) reports three QoS metrics (e.g.,
FER, SINR and ADC desense) there can be two additional fields 852,
854 (not illustrated) for reporting SINR measurements that are
similar to those for category 1 and two more additional fields 862,
864 (not illustrated) for reporting ADC desense measurements that
are also similar to those for category 1. In other words, following
the total categories field 830, for each QoS metric being reported
by the station, there are additional fields. With OFDMA, multiple
transmitters can simultaneously desense a receiver. A
destination/receiver station (B) can estimate ADC desense by
comparing the RSS measurements across all sub-channels of the
desired receive grant time slot(s). The difference between the
sub-channel with the maximum RSS power level and the desired
sub-channel RSS power provides an estimate of ADC desense. For
example, each 6 dB of power difference represents at least 1 bit
desense of the ADC. Intermodulation products may add more desense.
Additional details regarding one implementation of the fields of
the GMRM 800 are provided below in Table 4.
TABLE-US-00004 TABLE 4 Field Size Description RM ID # 1 byte
Specifies a unique identification number for this RM RM Size 1 byte
Specifies size in bytes of the RM Total 3 bits Identifies the total
number of measurements in Categories the remainder of the table.
Each measurement will contain 2 fields. Category 1 3 bits
Identifies which QoS measurement category Meas. Type applies for
the following measurement field 001: FER 010: SINR 100: ADC Desense
Category 1 5 bits Category 1 measurement Meas. Category 2 3 bits
Identifies which QoS measurement category Meas. Type applies for
the following measurement field 001: Cat 1: FER 010: Cat 2: SINR
100: Cat 3: ADC Desense Category 2 5 bits Category 2 measurement
Meas. . . . . . . . . .
Scheduling
[0113] Embodiments of the present invention generally relate to
protocols, methods and apparatus for scheduling uplink
communication resources within a cell of an OFDMA communication
system. For example, the disclosed embodiments can provide
MAC-layer scheduling methods and OFDMA scheduling apparatus for
scheduling uplink communication resources in time-division duplex
(TDD) or frequency division duplex (FDD) wide area wireless OFDMA
communication networks (e.g., WiMAX/IEEE 802.16, 3GPP Long Term
Evolution (LTE)).
[0114] More specifically, the disclosed protocols, methods and
apparatus allow for scheduling of (1) uplink communication
resources allocated for "normal" uplink communications from
stations to a base station and (2) uplink communication resources
allocated for "direct link" or peer-to-peer communication between
stations. The disclosed scheduling methods and apparatus allocate
uplink resources for "direct link" or peer-to-peer communication
between stations such that near-far issues caused by peer-to-peer
communication are reduced/avoided. The disclosed protocols, methods
and apparatus can prevent peer-to-peer communication links using
different sub-channels within the same time slot from creating
near-far issues for other receiver stations that are within
communication range. In other words, a base station schedules
uplink communication resources that are used by stations to avoid
scheduling resources in the same time slot such that near/far
issues result.
[0115] Some of the disclosed embodiments, that will now be
described below, relate to proactive scheduling methods for initial
uplink resource allocation. In such embodiments, a proactive
resource allocation method is provided in which a base station
instructs stations how to collect appropriate information. The
stations collect the information and send to the base station,
which then uses the information to create and update peer-sets of
the stations, and then schedules inter-peer resources and/or
intra-peer resources.
Proactive Scheduling Methods for Initial Uplink Resource
Allocation
[0116] FIG. 9 illustrates proactive scheduling method 900 for
scheduling and allocating uplink (UL) resources in accordance with
some embodiments. The proactive scheduling method describes acts
(e.g., processing and communicating) that stations (STA) and base
stations must do before the base station allocates uplink resources
to the stations for peer-to-peer communications with other peer
stations. In the proactive scheduling method, a base station (BS)
and a source/transmitter station (Z) both participate, and
therefore both have a proactive scheduler module (PSM). For sake of
clarity, the respective scheduler modules are referred to below as
a base station proactive scheduler module (BSPSM) and station
proactive scheduler module (STAPSM), respectively.
[0117] The proactive scheduling method 900 begins at step 905. At
step 910, the base station generates an RMIE (FIG. 5) and
broadcasts the RMIE to request peer information from stations that
receive the RMIE including the source/transmitter station (Z). In
one implementation, the RMIE includes information to inform
stations how many and what type of measurements to take for
specified performance metrics (e.g., RSS,
signal-to-interference-noise ratio (SINR)).
[0118] At step 920, the stations, including a source/transmitter
station (Z) that wants to request a resource allocation, determine
(measure or calculate) peer information (e.g., performance metrics)
being requested by the base station based on information specified
in the RMIE. At step 930, stations (including the
source/transmitter station (Z)) communicate a RMRM (FIG. 6) to the
base station. The RMRM includes peer information requested by the
base station in the RMIE as determined by the source/transmitter
station (Z). The source/transmitter station (Z) also transmits a
resource request message (RRM) to the base station to request
resources for a communication session or "call" with a
destination/receiver station (B).
[0119] At step 940, the base station processes the RMRM (and RMRMs
from other stations) and determines uplink resources to be
allocated to the source/transmitter station (Z) for its
communication with the destination/receiver station (B). In
summary, the base station uses the information in station RMRMs to
create rules for scheduling or allocating uplink resources to avoid
causing near-far issues. The uplink resources allocated to the
source/transmitter station (Z) are allocated such that stations
communicating over different sub-channels of the same time slot(s)
will not experience or cause near-far problems for other stations,
including the source/transmitter station (Z), and likewise
communications by the source/transmitter station (Z) over the
uplink resources it has been allocated will not cause near-far
problems for other stations.
[0120] For a given location, traffic characteristics may change
over time, with different concentrations of base station-to-station
and station-to-station traffic. As indicated by the feedback loop
exiting step 940 and returning to step 910, the proactive
scheduling methods can accommodate large changes over time in the
amount of peer-to-peer traffic by dynamically adjusting the content
of the RMIE and RMRM transmitted.
[0121] In the description of FIGS. 10 and 11 that follows,
processing performed at the source/transmitter station (Z) that is
requesting a new uplink resource grant from a base station will be
described. However, it will be appreciated that multiple
source/transmitter stations can simultanteously request new uplink
resource grants from the base station and that the base station can
simultaneously receive uplink resource request messages (RRMs) from
multiple stations. Accordingly, mutiple source/transmitting
stations can simultaneously perform the processing illustrated in
FIGS. 10 and 11, and a base station can simultaneously perform the
processing illustrated in FIGS. 12-15 for multiple
source/transmitter stations (Z).
[0122] FIG. 10 is flow chart illustrating processing 1000 of an
RMIE 500 during a proactive scheduling method 1000 in accordance
with some embodiments.
[0123] As noted above, the base station maintains a resource
allocation map, and at step 1010 regularly generates and broadcasts
an RMIE 500 (FIG. 5). The RMIE 500 specifies a Partial Resource
Allocation Map (PRAM) 530 that indicates portions of the resource
allocation map that the base station would like more information
about and would like the stations to provide more information
about.
[0124] Prior to requesting an uplink resource grant, the
source/transmitter station (Z) waits for the RMIE 500. When the
source/transmitter station (Z) receives the RMIE 500 at step 1020,
the method 1000 proceeds to step 1030, where the source/transmitter
station (Z) of the station decodes the PRAM 530 of the RMIE 500 to
determine which resource measurement variables are being requested
by the base station in the RMIE 500.
[0125] In general, the resource measurement variables specify what
information should be collected by the recipient stations. In one
implementation, the resource measurement variables specify
performance metrics (e.g., RSS) that are to be measured for
particular uplink resources indicated in the PRAM 530.
[0126] At step 1040, the source/transmitter station (Z) sets the
resource measurement variables and then processing then continues
as illustrated in FIG. 11.
[0127] FIG. 11 is flow chart illustrating processing 1100 performed
at a source/transmitter station (Z) during a proactive scheduling
method in accordance with some embodiments. In particular, FIG. 11
illustrates processing 1100 performed at a source/transmitter
station (Z) for measuring performance metrics (e.g., RSS)
corresponding to measurement variables for selected uplink
resources and then generating a resource map response message
(RMRM) 700 that is transmitted to the base station.
[0128] At step 1105, the source/transmitter station (Z) starts a
timer that specifies a resource measurement period, and begins to
monitor an OFDMA channel for selected ones (or all of) the uplink
resources specified in the RMIE 500 received from the base station.
The resource measurement period is set such that the
source/transmitter station (Z) will receive one or more OFDMA
frames 400 transmitted on the OFDMA channel. The resource
measurement period can be a standard value that is known to the
source/transmitter station (Z) that is of a long enough duration to
allow accurate measurements. This duration can vary depending upon
the implementation. In one embodiment the resource measurement
period is selected during system installation and downloaded to all
stations.
[0129] At step 1110, the source/transmitter station (Z) monitors an
OFDMA channel until it receives a new OFDMA frame 400 from the base
station. The OFDMA frame 400 includes a preamble which defines when
the OFDMA frame 400 starts.
[0130] Upon receiving the next OFDMA frame 400, at step 1120, the
station begins determining (e.g., measuring and/or calculating)
performance metrics for "selected" uplink resources specified in
the PRAM 530 received from the BS. The stations do not need to
determine (e.g., measure and/or calculate) performance metrics for
all uplink resources specified in the PRAM 530, but can in some
implementations. In some embodiments, the recipient stations are
permitted to select particular ones of the uplink resources
specified in the PRAM 530. For example, in one embodiment of step
1120, the source/transmitter station(i.e., a particular station
that plans to request an uplink resource allocation from the BS)
can select particular ones of the uplink resources specified in the
PRAM 530, and monitor those selected uplink resources to determine
performance metrics (e.g., RSS) associated with those selected
uplink resources. In such embodiments, the portion of the PRAM 530
that is monitored is left up to the station. In one specific
implementation, the station can randomly select uplink resources
from the PRAM 530 or randomly select groups of uplink resources
from the PRAM 530 to monitor. As will be described below, the
performance metrics will eventually be used to generate a partial
resource measurement map (PRMM) 740.
[0131] In one implementation of step 1120, the source/transmitter
station (Z) measures receive signal strength (RSS) levels for the
selected uplink resources. Each of the uplink resources is a
combination of a time slot and frequency sub-channel. For each time
slot of a selected uplink resource (i.e., that the
source/transmitter station (Z) selects from the PRAM 530), the
station scans all sub-channels in that time slot, down converts to
baseband, filters then takes the fast Fourier Transform (FFT). The
magnitude square of the output of the FFT is the power level for
each frequency sub-carriers. The RSS of a given sub-channel is
obtained by summing the power of the sub-carriers that make up that
sub-channel. Each of the measured RSS values can be specified using
a received signal strength indicator (RSSI), which is a measure of
the received radio signal strength over a particular communication
link.
[0132] At step 1130, the source/transmitter station (Z) categorizes
the measured performance metrics into different categories. For
instance, according to one implementation, the source/transmitter
station (Z) categorizes the measured receive signal strength (RSS)
levels into different categories (e.g., high, middle and low
measured RSS levels).
[0133] At step 1140, the source/transmitter station (Z) determines
whether the resource measurement period has expired. If not, then
process 1100 loops back to step 1110.
[0134] If the resource measurement period has expired, then the
process 1100 proceeds to step 1150, where the source/transmitter
station (Z) uses the performance metrics it determined (measured or
calculated) to generate a resource map response message (RMRM) 700
that includes a partial uplink resource measurement map (PRMM) 740
for uplink resources specified in the PRAM 530 that are selected by
the source/transmitter station (Z). The PRMM includes performance
metrics determined by the the source/transmitter station (Z) for
selected uplink resources (time slot/frequency sub-channel). In the
embodiment described above with reference to FIG. 6, the partial
uplink resource measurement map (PRMM) 740 includes RSS measurement
information measured by the source/transmitter station (Z) for at
least some of the uplink resources specified in the RMIE 500, and
the partial uplink resource measurement map (PRMM) 740 groups this
RSS measurement information into different categories, which in one
example, are high, middle and low measured RSS levels.
[0135] Stations can then transmit their respective RMRMs back to
the base station. At a minimum, any station that is preparing to
request an uplink resource allocation needs to send its RMRM. Thus,
at step 1150, the source/transmitter station (Z) transmits the RMRM
700 to the base station to report its performance metrics (e.g.,
RSS measurements measured/determined by the source/transmitter
station (Z)) to the base station via the PRMM 740. At a maximum,
every station receiving the RMIE sends its RMRM to the base
station. As will be described below with reference to FIG. 12, the
base station can then use the PRMM 740 (along with other
information including PRMMs from other stations) to help make
uplink resource allocation decisions.
[0136] At step 1150, the source/transmitter station (Z) also
transmits an initial uplink Resource Request Message (RRM) to the
base station. The RRM indicates the type of communication session
the source/transmitter station (Z) would like to set up with a
destination/receiver station (B) including information regarding
QoS requirements for that communication session. The Resource
Request Message (RRM) can include information including: (1) the
type of communication session the source/transmitter station (Z)
would like to set up with a destination/receiver station (B)
including information regarding QoS requirements for that
communication session, (2) information regarding the station type,
(3) information about the size of the packet to be transmitted by
the source/transmitter station (Z), etc.
[0137] In one embodiment, the RRM also includes the RMRM 700 (and
hence the PRMM 740). In another embodiment, the source/transmitter
station (Z) transmits the RMRM 700 separately.
[0138] FIG. 12 is flow chart illustrating processing 1200 performed
at a base station during a proactive scheduling method in
accordance with some embodiments.
[0139] At step 1210, the base station receives the resource map
response message (RMRM) 700 and the initial uplink Resource Request
Message (RRM) from the source/transmitter station (Z), and saves
this information in memory. Although not illustrated, the base
station can also receive RMRMs from other stations. As will be
described below, the base station eventually uses the RMRM received
from the source/transmitter station (Z) (along with RMRMs from
other stations) to schedule uplink resources allocated to the
source/transmitter station (Z).
[0140] At step 1215, the base station can determine, based on the
RMM, the packet size the source/transmitter station (Z) requests to
transmit and/or the station type of the station that is requesting
an uplink resource grant (i.e., the source/transmitter station
(Z)), needed to determine the amount of resources to be
allocated.
[0141] At step 1225, based on the partial resource measurement map
(PRMM) 740 from the RMRM 700, the base station updates peer
information for the source/transmitter station (Z) that is
requesting the uplink resource grant. At this point in time, only
information that station Z has sent in the recent RMRM is used to
update Zs peer information. However, other stations that receive
transmissions from Z may send back Zs resource allocation in their
RMRM. Some embodiments may assume that wireless channels are
reciprocal and update Zs peer information to include stations whose
RMRMs contain Z. One embodiment of the peer information updating
method will be described below with reference to FIG. 13.
Update of Peer Information
[0142] FIG. 13 is flow chart illustrating a method 1300 performed
at a base station for updating peer information for a
source/transmitter station (Z) that is requesting the uplink
resource grant during a proactive scheduling method in accordance
with some embodiments. As noted above, the source/transmitter
station (Z) determines peer information by scanning over a PRAM 530
of the resource allocation map, and sends a RMRM 700 to the base
station that includes the peer information in map coordinates. In
the example that will be described below, source/transmitter
station (Z) specifies resources in the resource allocation map
where the interference levels are high and low. For instance, in
this simplified example, the source/transmitter station (Z) has
determined that it has high RSS peers at X1, X2 and X3, where X1,
X2 and X3 are each locations in the resource map, and has
determined that it has low RSS peers at Y1, Y2 and Y3, where Y1, Y2
and Y3 are other locations in the resource map. (X1 is sub-channel
1 and time slot 3). Thus, in the description that follows an
example is described in which the source/transmitter station (Z)
reports three peers {X.sub.1, X.sub.2, X.sub.3} with high measured
RSS values (Z.sub.HI.sub.--.sub.meas) and three peers {Y.sub.1,
Y.sub.2, Y.sub.3} with low measured RSS values
(Z.sub.LO.sub.--.sub.meas), and zero peers with medium RSS values
(Z.sub.MED.sub.--.sub.meas). As will now be described, in this
embodiment, the base station extracts measured RSS information for
each peer station from the partial resource measurement map (PRMM)
740 of the RMRM 700 that was received from the source/transmitter
station (Z) to create an entry in a peer memory map (PMM) for
station Z that is illustrated in row 1 of Table 5.
[0143] At step 1310, the base station translates or converts the
resource information (X.sub.1, Y.sub.1, etc . . . ) from
source/transmitter station (Z) (that was provided in the partial
resource measurement map (PRMM) 740) into actual peer station
identification numbers or "identifiers" (x.sub.1, y.sub.1, etc . .
. ). Because the base station generated the resource allocation
map, the base station knows which station was previously assigned
to which resource (i.e., the base station know which resources were
allocated to what stations). Hence, given the resource location
(sub-channel/time-slot), the base station knows the station
identification number that was allocated to transmit during the
given resource. For example, when the base station receives
resource allocation X.sub.1 (for instance frequency sub-channel 1
and time slot 3 above)in a PRMM, the base knows that device x1 was
previously assigned to transmit during this portion of the frame
400 using this resource allocation.
[0144] At step 1320, for each of the peer identifiers determined at
step 1310, the base station evaluates the corresponding category
MAP Data fields 748, 758, 768 from the PRMM 740, determines which
peer station indentification numbers correspond to particular
entries in each of the category MAP Data fields 748, 758, 768, and
determines the appropriate transmitter peer list for each peer
station identification number. A base station may maintain multiple
transmitter peer lists for high power RSS peers, medium power RSS
powers and low power RSS peers. Low power RSS peers can be referred
to as transmitting non-peers. For instance, in one simplified
example, after completing step 1320 the base station has determined
that source/transmitter station with identification number z has
high RSS peer stations with identification numbers x.sub.1, x.sub.2
and x.sub.3, low RSS peer stations with identification numbers
y.sub.1, y.sub.2 and y.sub.3, and no medium RSS peer stations.
[0145] At step 1330, the base station then creates or updates an
entry in a Peer Memory Map (PMM) for source/transmitter station
(Z). The PMM includes columns and rows, where each row corresponds
to data for a particular station. In the example illustrated, the
PMM includes three columns as follows: (1) one column that lists
stations including the source/transmitting station (with
identification number z) and every other station that can
potentially engage in peer to peer communications, (2) another
column that lists peer stations (of each station in the first
column) having a high RSS and (3) another column that lists peer
stations (of each station in the first column) having a low RSS.
Although not illustrated, there can be another column that lists
peer stations (of each station in the first column) having a medium
RSS. An entry in the PMM is a row of data for a particular station
that is identified in the first column.
[0146] One example of a PMM is illustrated in Table 5 below. In
this simplified example, the Peer Memory Map (PMM) in Table 5 has
entries for two stations: source/transmitter station (z) and the
destination/receiver station (b). For destination/receiver station
(b) the PMM includes a list of peer stations (a.sub.1, a.sub.2,
a.sub.3) having a high measured RSS and a list of peer stations
(w.sub.1, w.sub.2, w.sub.3) having a low measured RSS, where
a.sub.1, a.sub.2 and a.sub.3 and w.sub.1, w.sub.2, w.sub.3 are peer
station identification numbers. Similarly, for the
source/transmitter station (z) the PMM includes a list of peer
stations (x.sub.1, x.sub.2, x.sub.3) having a high measured RSS and
a list of peer stations (y.sub.1, y.sub.2, y.sub.3) having a low
measured RSS, where x.sub.1, x.sub.2 and x.sub.3 and y.sub.1,
y.sub.2, y.sub.3 are peer station identification numbers. Although
not illustrated in Table 5, the PMM includes one entry for each
station that can potentially engage in peer to peer communication.
After updating the source/transmitter station PMM entries for z and
b in Table 5, the peers for z and b may also be updated. For
example in Table 5 the PMM entries for stations (x.sub.1, x.sub.2,
x.sub.3) all can have station z listed as a high power peer and
stations (a.sub.1, a.sub.2, a.sub.3) can have station b listed as a
high power peer. (Table 5 does not show the analogous low power
peers for stations (y.sub.1, y.sub.2, y.sub.3) and (w.sub.1,
w.sub.2, w.sub.3)).
TABLE-US-00005 TABLE 5 Peer Memory Map (PMM) Peer Stations Peer
Stations Having Having Station High Measured RSS Low Measured RSS
source/transmitter station (z) x.sub.1 x.sub.2 x.sub.3 y.sub.1
y.sub.2 y.sub.3 destination station (b) a.sub.1 a.sub.2 a.sub.3
w.sub.1 w.sub.2 w.sub.3 . . . STA (x.sub.1) z . . . . . . . . . . .
. . . . STA (x.sub.2) z . . . . . . . . . . . . . . . STA (x.sub.3)
z . . . . . . . . . . . . . . . STA (a.sub.1) b . . . . . . . . . .
. . . . . STA (a.sub.2) b . . . . . . . . . . . . . . . STA
(a.sub.3) b . . . . . . . . . . . . . . . . . .
Generation of Updated Peer Sets
[0147] High RSS peer stations cause the most interference for
nearby receivers, and therefore it is desirable to isolate
transmissions of high RSS peer stations in the time domain by
scheduling transmission of the source/transmitter station (Z) so
that they are received at a time when it's high RSS peer stations
are not transmitting.
[0148] The base station receives PRMMs from each station that want
to transmit peer-to-peer (or station-to-station) traffic. The base
station combines the information from multiple PRMMs received from
different stations to create or update peer sets. In the following
description, different peer sets will be called high and low impact
peer sets. For example, as illustrated at step 1230 of FIG. 12, the
base station processes the partial resource measurement map (PRMM)
740 provided in the RMRM 700 along with other PRMMs provided in
RMRMs from other stations to generate or update "high impact peer
sets" of stations that have a high probability of causing near-far
issues to each other and "low impact peer sets" that have a low
probablity of causing near-far issues to each other. As used
herein, the term "high impact peer set" refers to information that
identifies groups of stations that could potentially cause near-far
issues if one station that belongs to the peer set transmits while
another station that belongs to the peer set is attempting to
receive a different transmission from another station that does not
belong to the peer set. As used herein, the term "low impact peer
set" refers to information that identifies groups of stations that
are unlikely to cause near-far issues if one station that belongs
to the peer set transmits while another station that belongs to the
peer set is attempting to receive a different transmission from
another station that does not belong to the peer set. It should be
noted that interference within a time slot may be additive such
that two or more medium impact peers can cause high impact.
[0149] For instance, in the example described above, the
source/transmitter station (Z) has three high impact (high RSS)
peer stations: Z.sub.HI.sub.--.sub.meas={x.sub.1, x.sub.2, x.sub.3}
and three low impact peer stations
Z.sub.LO.sub.--.sub.meas={y.sub.1, y.sub.2, y.sub.3}. Similarly,
the destination/receiver station (B) has three high impact peers:
B.sub.HI.sub.--.sub.meas={a.sub.1, a.sub.2, a.sub.3} and three low
impact peers B.sub.LO.sub.--.sub.meas={w.sub.1, w.sub.2,
w.sub.3}.
Marking Timeslots as Excluded or Preferred Based on Transmit and
Receive Peer Sets
[0150] Continuing with FIG. 12, at step 1240, after peer sets are
updated, the base station determines which time slots are excluded
(TS.sub.x) and preferred (TS.sub.p) based on the current station
resource assignments in each time slot, the transmitter's peer sets
in the base station PMM and the receiver's peer sets in the base
station PMM, and then marks potential time slots in an uplink
portion 450 of the resource allocation map maintained at the base
station.
[0151] FIG. 14 is flow chart illustrating processing 1400 performed
at a base station for determining which time slots of the resource
allocation map are to be marked excluded time slots (TS.sub.x) and
preferred time slots (TS.sub.p) during a proactive scheduling
method in accordance with some embodiments. The base station
calculates excluded time slots (TS.sub.x) and preferred time slots
(TS.sub.p) by comparing stations already in these time slots with
peer sets of the source/transmitter (Z) and peer sets of the
destination/receive station (B).
[0152] At step 1410, per Equation (1), the base station marks time
slots that include peers {a.sub.1, a.sub.2, a.sub.3} in the high
impact (high RSS) peer set (B.sub.HI.sub.--.sub.meas) of the
destination/receiver station (B) as excluded time slots
(TS.sub.x):
TS.sub.x={TS(i): i .epsilon. B.sub.HI.sub.--.sub.meas) (Equation
1),
[0153] where .epsilon. denotes "belongs to" and TS(i) represents
the time slot in which transmission by station i has already been
scheduled.
[0154] At step 1420, per Equation (2), the base station marks time
slots that include peers {x.sub.1, x.sub.2, x.sub.3} in the high
RSS peer set (Z.sub.HI.sub.--.sub.meas) of the source/transmitter
station (Z) as preferred time slots (TS.sub.p):
TS.sub.p={TS(i): i .epsilon. Z.sub.HI.sub.--.sub.meas) (Equation
2).
[0155] At step 1430, per Equation (3), if there are no peers in the
high RSS peer set (Z.sub.HI.sub.--.sub.meas) of the
source/transmitter station (Z), then the base station marks time
slots that include peers {w.sub.1, w.sub.2, w.sub.3} in the low
impact (low RSS) peer set (B.sub.LO.sub.--.sub.meas) of the
destination/receiver station (B) as preferred time slots
(TS.sub.p):
TS.sub.p={TS(i): i .epsilon. B.sub.LO.sub.--.sub.meas) (Equation
3).
[0156] With intra-peer-set communications or in the presence of
shadow fading, some time slots can be marked as being both an
excluded time slot (TS.sub.x) and preferred time slot (TS.sub.p).
Specifically, if j is a transmit station assigned to time slot
TS(j) such that: j .epsilon. Z.sub.HI.sub.--.sub.meas and j
.epsilon. B.sub.HI.sub.--.sub.meas, then TS(j) will be marked as
being both an excluded time slot (TS.sub.x) and preferred time slot
(TS.sub.p).
[0157] This conflicting time slot status can be resolved based on
whether the source/transmitter station (Z) is a member of the high
impact peer set (B.sub.HI.sub.--.sub.meas) of the
destination/receiver station (B) (i.e., Z .epsilon.
B.sub.HI.sub.--.sub.meas) as indicated in Equation (4) below.
If Z .epsilon. B.sub.HI.sub.--.sub.meas, mark (TS(j) as preferred
(TS.sub.p), else mark (TS(j) as excluded (TS.sub.x) (Equation
4)
[0158] If Z is a member of the high impact peer set
(B.sub.HI.sub.--.sub.meas) of the destination/receiver station (B)
(i.e., Z .epsilon. B.sub.HI.sub.--.sub.meas), then the time slot
occupied by node j TS(j) is marked as preferred. Otherwise, TS(j)
is marked as excluded.
[0159] In the former situation, the source/transmitter station (Z),
the destination/receiver station (B), and transmit station (j) are
all high-power peers of each other. The intra-peer set
communication from the source/transmitter station (Z) to the
destination/receiver station (B) is power controlled to use the
minimum power needed to achieve the system's maximum modulation
rate. The destination/receiver station (B) receives a high RSS
level and can tolerate the presence of transmissions from transmit
station (j) in the same vicinity. The latter situation can arise
with shadow fading when the source/transmitter station (Z) is not a
high-power peer of the destination/receiver station (B) but
transmit station (j) is a high-power peer of the source/transmitter
station (Z) and the destination/receiver station (B). This can
happen, for example, if the source/transmitter station (Z) and the
destination/receiver station (B) are in adjacent rooms separated by
a wall and transmit station (j) is at the doorway connecting the
two rooms.
[0160] At step 1250, the base station estimates the uplink resource
allocation size (RAS) based on the channel quality, i.e., estimated
SINR for the resources under consideration (which determines the
modulation and coding scheme that can be used) and the packet size.
Thus, different RASs may be needed in different sub-channels, for
example due to different fading and interference conditions. The
uplink resource allocation size (RAS) depends on the
channel/interference conditions experienced by the
destination/receiver station (B) on the particular sub-channel(s).
Thus, the RAS may change depending on which sub-channel/sub-channel
group is considered for allocation. That is, the RAS is not
necessarily the same for all parts of the wideband channel.
[0161] Specifically, starting with the first preferred time slot
(TS.sub.p) and the first candidate set of sub-channels, the number
of sub-channels required and the transmit power required are
computed. If the number of sub-channels available in the first
preferred time slot (TS.sub.p) is inadequate, the next preferred
time slot (TS.sub.p) is considered and so on. Any preferences
pertaining to horizontal and vertical striping can be applied.
[0162] At step 1260, the base station allocates one or more uplink
resources to the source/transmitter station (Z). Each "resource" is
a combination of a frequency sub-channel within a particular time
slot of an OFDMA frame 400. The set of one or more uplink resources
allocated to the source/transmitter station (Z) is a "resource
allocation" that can be any combination of one or more preferred
time slot (TS.sub.p) and any combination of one or more
subcarriers/sub-channels within the one or more preferred time
slots (TS.sub.p). In one embodiment, the right-most preferred time
slot(s) (TS.sub.p) in the UL portion 450 of the resource allocation
map, which are also not marked as being excluded time slots
(TS.sub.x), are allocated to the source/transmitter station
(Z).
[0163] After the base station allocates the uplink resources to the
source/transmitter station (Z), at step 1270 the base station
transmits a resource grant message (RGM) to the source/transmitter
station (Z) to notify the source/transmitter station (Z) of the
uplink resources allocated to it. The source/transmitter station
(Z) may then use the allocated uplink resources specified in the
RGM for tranmissions to the destination/receiver station (B).
Reactive Scheduling Methods for Potential Reallocation of Uplink
Resources Based on QoS Performance Metrics for a Communication
Session
[0164] In the proactive method, uplink resources are allocated to
the source/transmitter station (Z). In some scenarios, after a
communication session or call is in progress, the uplink resource
allocations provided via the proactive scheduling method can become
inadequate and near-far issues can occur for the
destination/receiver station (B). In such cases, the
destination/receiver station (B) should request a new uplink
resource allocation (or "re-allocation") to reduce and/or eliminate
such near-far issues. For instance, in one implementation, a
resource grant is terminated, renewed or reallocated at regular
intervals (e.g., approximately every 2 seconds).
[0165] Reactive scheduling methods will now be described that can
be used to address such scenarios. The reactive scheduling methods
describe actions performed by a base station and a station after a
communication session or call is in progress. The reactive
scheduling methods allow for potential re-allocation of long-term
uplink resources based on QoS performance metrics. These reactive
scheduling methods allow the destination/receiver station (B) to
recover from scenarios in which the proactive scheduling methods
fail for some reason (e.g., station mobility or poor RSS
measurements). In such embodiments, a reactive uplink resource
allocation method is provided in which the base station
re-schedules uplink communication resources and possibly changes
the amount of information stations collect.
[0166] FIG. 15 is a flowchart illustrating a reactive scheduling
method 1500 in accordance with some embodiments. In this example,
the source/transmitter station (Z) is involved in a communication
session or call with the destination/receiver station (B) using
resources granted or allocated to it by the base station as part of
a proactive scheduling method. In the description that follows,
these currently granted resources being used in the active
communication session will be referred to below as "existing"
resources.
[0167] The reactive scheduling method 1500 starts at step 1505 when
destination/receiver station (B) begins a new peer-to-peer (or
station-to-station) communication session with the
source/transmitter station (Z). At step 1510, the
destination/receiver station (B) receives a Grant Metric
Information Element (GMIE) 600 generated and broadcast by the base
station. As described above, the GMIE 600 informs stations of the
type and amount of QoS information the destination/receiver
stations (B) are to provide to the base station via a Grant Metric
Response Message (GMRM) 800.
[0168] At step 1520, the destination/receiver station (B) decodes
the GMIE 600, determines QoS performance metrics (e.g., frame error
rate (FER), SINR, ADC desense) being requested by the base station
for existing uplink resources allocated to this communication
session, and determines (measures and/or calculates) those QoS
performance metrics for the existing uplink resources allocated to
this communication session that it is using to communicate with the
source/transmitter station (Z).
[0169] At step 1530, the destination/receiver station (B) can
determine, based on these QoS performance metrics, whether to
continue with its existing uplink resource allocation for this
communication session, or whether to request a new uplink resource
allocation for this communication session. For example, the
destination/receiver station (B) determines, based on the QoS
performance metrics (e.g., frame error rate (FER), SINR, ADC
desense) that it has measured/calculated for existing uplink
resources allocated to this communication session, whether to
continue using existing uplink resource allocation or whether to
request an adjustment or "reallocation" of the existing uplink
resources is necessary to prevent near/far problems.
[0170] When the destination/receiver station (B) determines, based
on the measured/calculated QoS performance metrics for existing
uplink resources allocated to this communication session, that
continued use of its existing uplink resources is likely to cause
near/far problems, the method 1500 proceeds to step 1540, where the
destination/receiver station (B) unicasts a GMRM to the base
station along with a request for a new uplink resource allocation
for this communication session with the source/transmitter station
(Z). At step 1550, in response to the request for a new uplink
resource allocation, the base station determines a new uplink
resource allocation and communicates this information to the
destination/receiver station (B) and the source/transmitter station
(Z).
[0171] By contrast, when the destination/receiver station (B)
determines that it would like to continue using existing uplink
resource allocation for its communication session with the
source/transmitter station (Z), the method 1500 proceeds to step
1565, where the destination/receiver station (B) renews the
allocation of its existing resources by transmitting a resource
renewal request message (RRRM) to the base station.
[0172] A specific implementation of the reactive scheduling method
will now be described with reference to FIGS. 16-18.
[0173] FIGS. 16-18 describe an embodiment of the reactive scheduler
that can use short term QoS metrics and/or long term QoS metrics
provided by the destination/receiver station (B) to create rules
for rescheduling uplink resource allocations to avoid causing
near-far issues. The base station can then allocate new uplink
resources to the source/transmitter station (Z) and the
destination/receiver station (B) for continuing their communication
session. This way, the base station can improve a new uplink
resource allocation to the source/transmitter station (Z) and the
destination/receiver station (B) since the base station bases this
new uplink resource allocation on feedback provided by the
destination/receiver station (B) at the time of the uplink resource
request.
[0174] FIG. 16 is a flowchart illustrating processing 1600
performed by a destination/receiver station (B) performs to
determine whether to request a new uplink resource allocation
during a reactive scheduling method in accordance with some
embodiments.
[0175] While participating in an active communication session or
call with the source/transmitter station (Z) over an existing
resource allocation, the destination/receiver station (B) actively
monitors the OFDMA channel. For each OFDMA frame 400 received, the
destination/receiver station (B) determines information the base
station has requested via a RMIE 500 and a GMIE 600. As described
below, the destination/receiver station (B) can measure any number
of QoS performance metrics with respect to the existing resources
that reflect quality of the communication link between the
source/transmitter station (Z) and the destination/receiver station
(B), and then use these QoS performance metrics to monitor adequacy
of the current uplink resource allocation.
[0176] The reactive scheduling method 1600 starts at step 1605,
when destination/receiver station (B) begins a new communication
session with the source/transmitter station (Z). At step 1610, the
destination/receiver station (B) receives a Resource Map
Information Element (RMIE) 500 and a Grant Metric Information
Element (GMIE) 600 generated and broadcast by the base station. The
RMIE and GMIE may be independent broadcast signals or may be
embedded in the control time slots at the beginning of an OFDMA
frame 400. The RMIE directs the destination/receiver station (B) to
collect information about its local environment. If the current
resource allocation that is being used for the communication
session begins performing poorly from a QoS perspective, it is
desirable for the base station to have up-to-date RSS measurement
information to use in making a new resource allocation. The
destination/receiver station (B) can send an RMRM to the base
station to provide this up-to-date RSS measurement information.
[0177] At step 1620, the destination/receiver station (B) decodes
the RMIE 500 and implements methods similar to those described
above with respect to FIG. 11 to measure RSS over a PRMM 740. The
destination/receiver station (B) also decodes the GMIE 600,
determines QoS performance metrics (e.g., frame error rate (FER),
SINR, ADC desense) being requested by the base station for existing
uplink resources allocated to this communication session, and
determines (measures and/or calculates) "short-term" QoS
performance metrics for the existing uplink resources allocated to
this communication session that it is using to communicate with the
source/transmitter station (Z). Short-term QoS performance metrics
are QoS performance metrics that are determined
(measured/calculated) over the current OFDMA frame 400.
[0178] At step 1630, the destination/receiver station (B) can
determine whether the short-term QoS performance metrics are
acceptable for the current OFDMA frame 400.
[0179] If the short-term QoS performance metrics are not acceptable
for the current OFDMA frame 400, the method 1600 proceeds to step
1670, where the destination/receiver station (B) can send a GMRM to
the base station that reports the short-term QoS performance
metrics that were determined at step 1620, a RMRM and an uplink
resource re-allocation request message (RRARM) to request new
uplink resource allocation for the communication session between
the source/transmitter station (Z) and the destination/receiver
station (B). Although not illustrated in FIG. 16, in one
embodiment, the destination/receiver station (B) can abort the
existing resources before the resource period ends if a short-term
QoS metric (e.g. frame error rate (FER)) exceeds a threshold and
send the base station a RMRM identifying alternative resource
allocation information and a GMRM that identifies the QoS
performance metric that caused the resource abort.
[0180] If the short-term QoS performance metrics are acceptable for
the current OFDMA frame 400, the method 1600 proceeds to step 1640,
where the destination/receiver station (B) can determine if the
grant period for the existing resources has expired. Grant periods
can be a function of traffic type, channel reliability, traffic
intensity and base station loading. Grant periods may also be
values specified by standard bodies for certain types of traffic.
If the grant period for the existing resources has not yet expired,
then the method 1600 loops back to step 1610, where the
destination/receiver station (B) can continue to monitor short-term
QoS performance metrics until the grant period for the existing
resources expires.
[0181] If the grant period for the existing resources has expired,
then the method 1600 can proceed to step 1645, where the
destination/receiver station (B) can send a RMRM 700 and a GMRM 800
to the base station that reports the short-term QoS performance
metrics for this OFDMA frame 400, and the method 1600 proceeds to
step 1650 where the destination/receiver station (B) can determine
whether there is more data for this communication session (or
call).
[0182] If the destination/receiver station (B) determines that
there is no more data for this communication session (or call),
then the method 1600 ends at step 1655.
[0183] If the destination/receiver station (B) determines that
there is more data for this communication session (or call), then
the method 1600 proceeds to step 1660, where the
destination/receiver station (B) can determine whether the
long-term QoS performance metrics are acceptable. This way the
destination/receiver station (B) can determine whether it wants to
continue using its existing uplink resource allocation for this
communication session, or whether to request a new uplink resource
allocation for this communication session (i.e., an adjustment or
"reallocation" of the existing uplink resources is necessary to
prevent near/far problems).
[0184] The long-term QoS performance metrics are determined by
processing QoS measurements. For instance, one embodiment estimates
long-term QoS metrics as the running average of the short-term QoS
performance metrics (determined for each frame) from the start of a
grant period up to the current point in time. The
destination/receiver station (B) compares the long-term metrics
over the grant period with thresholds to determine whether or not a
re-association request should be made. In one embodiment, the FER
threshold for triggering re-association request from a
destination/receiver station (B) depends on the type of traffic
being communicated since different traffic types require different
quality of service (QoS) and therefore need different
re-association thresholds. For example, best effort data can
tolerate fairly high FER, while real time traffic is more sensitive
to interference. When the QoS Traffic Type is known, the table
below provides re-associating trigger points according to one
implementation.
TABLE-US-00006 TABLE 6 Re-association Trigger Points QoS/ FER
Traffic Type Trigger Level Best Effort Data 20% Voice 5% Video
3%
[0185] When the ADC desense exceeds a predefined tolerance limit,
RSS levels for all uplink resources causing ADC desense to the
receiver's desired grant can be returned in the RMRM when a
destination/receiver station (B) requests re-association.
[0186] If the long-term QoS performance metrics are acceptable, the
method 1600 proceeds to step 1665, where the destination/receiver
station (B) can renew the allocation of its existing resources by
transmitting a resource renewal request message (RRRM) to the base
station. In other words, the destination/receiver station (B) can
request renewal of its current uplink resource allocations so that
it can continue using existing uplink resource allocation for its
communication session with the source/transmitter station (Z).
[0187] If the long-term QoS performance metrics for existing uplink
resources (allocated to this communication session) are not
acceptable (e.g., that continued use of its existing uplink
resources is likely to cause near/far problems), the method 1600
proceeds to step 1670, where the destination/receiver station (B)
can unicast a GMRM to the base station that reports the long-term
QoS performance metrics (as computed above), a RMRM, and an uplink
resource re-allocation request message (RRARM) to request new
uplink resource allocation for its communication session with the
source/transmitter station (Z). In response to the uplink resource
re-allocation request message, the base station can determine new
uplink resources to allocate for the communication session between
the source/transmitter station (Z) and the destination/receiver
station (B).
[0188] FIG. 17 is flow chart illustrating processing 1700 performed
at a base station during a reactive scheduling method in accordance
with some embodiments.
[0189] At step 1710, the base station receives the resource map
response message (RMRM) 700, a grant metric response message (GMRM)
800 and the uplink Resource Re-allocation Request Message (RRARM)
from the destination/receiver station (B), and saves this
information in memory. Although not illustrated, the base station
can also receive RMRMs and GMRMs from other stations. As will be
described below, the base station eventually uses the RMRM and the
GMRM received from the destination/receiver station (B) (along with
RMRMs and GMRMs from other stations) to schedule uplink resources
allocated for the communication session between the
source/transmitter station (Z) and the destination/receiver station
(B).
[0190] At step 1715, the base station can determine, based on the
RRARM, the packet size the destination/receiver station (B)
requests to transmit and/or the station type of the station that is
requesting an uplink resource re-allocation (i.e., the
destination/receiver station (B)). The packet size can be used to
determine the amount of resources to be allocated (e.g. number of
frequency sub-channels and number of time slots).
[0191] At step 1725, based on the partial resource measurement map
(PRMM) 740 from the RMRM 700, the base station updates peer
information for the destination/receiver station (B) that is
requesting the uplink resource re-allocation. Moreover, in some
embodiments other RMRM information can be used to update the
source/transmitter station's (Z) peer sets. In addition, timeouts
may be used for each individual peer to allow past PRMM 740
measurements to reside in the peer set memory for a period of time.
The reactive scheduling method uses techniques similar to those
used in the proactive scheduling method to improve peer sets. One
embodiment of the peer information updating method will be
described below with reference to FIG. 18.
Update of Peer Information
[0192] FIG. 18 is flow chart illustrating a method 1800 performed
at a base station for updating peer information for the
destination/receiver station (B) that is requesting the uplink
resource re-allocation during the reactive scheduling method in
accordance with some embodiments. As noted above, the
destination/receiver station (B) determines peer information by
scanning over a PRAM 530 of the resource allocation map, and sends
a RMRM 700 to the base station that includes the peer information
in map coordinates. In the example that will be described below,
destination/receiver station (B) specifies resources in the
resource allocation map where it determines high level RSS, medium
level RSS and low level RSS. For instance, in this simplified
example, the destination/receiver station (B) has determined that
it has high RSS peers at A1, A2 and A3, where A1, A2 and A3 are
each locations in the resource map, and has determined that it has
low RSS peers at W1, W2 and W3, where W1, W2 and W3 are other
locations in the resource map. (W1 is sub-channel 1 and time slot
3). Thus, in the description that follows an example is described
in which the destination/receiver station (B) reports three peers
with identification numbers {a.sub.1, a.sub.2, a.sub.3} with high
measured RSS values (B.sub.HI.sub.--.sub.meas) and three peers with
identification numbers {w.sub.1, w.sub.2, w.sub.3} with low
measured RSS values (B.sub.LO.sub.--.sub.meas), and zero peers with
medium RSS values (B.sub.MED.sub.--.sub.meas). As will now be
described, in this embodiment, the base station extracts measured
RSS information for each peer station from the partial resource
measurement map (PRMM) 740 of the RMRM 700 that was received from
the destination/receiver station (B) to create or update an entry
in a peer memory map (PMM) for destination/receiver station (B)
that is illustrated in row 2 of Table 7.
[0193] At step 1810, the base station translates or converts the
resource information (A.sub.1, W.sub.1, etc . . . ) from
destination/receiver station (B) (that was provided in the partial
resource measurement map (PRMM) 740) into actual peer station
identification numbers or "identifiers" (a.sub.1, w.sub.1, etc . .
. ). Because the base station generated the resource allocation
map, the base station knows which station was previously assigned
to which resource (i.e., the base station know which resources were
allocated to what stations). Hence, given the resource location
(sub-channel/time-slot), the base station knows the station
identification number that was allocated to transmit during the
given resource. For example, when the base station receives
resource allocation Al in a PRMM, the base station knows that
device a.sub.1 was previously assigned to resource allocation
A.sub.1 (frequency sub-channel 1 and time slot 3 above).
[0194] At step 1820, for each of the peer identifiers determined at
step 1810, the base station evaluates the corresponding category
MAP data fields 748, 758, 768 from the PRMM 740, determines which
peer station identificiation numbers correspond to particular
entries in each of the category MAP data fields 748, 758, 768, and
determines the appropriate transmitter peer list for each peer
station identifier. A base station may maintain multiple
transmitter peer lists for high power RSS peers, medium power RSS
powers and low power RSS peers. Low power RSS peers can be referred
to as transmitting non-peers. For instance, in one simplified
example, after completing step 1820 the base station has determined
that destination/receiver station (B) with identification number b
has high RSS peer stations with identification numbers a.sub.1,
a.sub.2 and a.sub.3 and low RSS peer stations with identification
numbers w.sub.1, w.sub.2 and w.sub.3, and no medium RSS peer
stations.
[0195] At step 1830, the base station then creates or updates an
entry in a Peer Memory Map (PMM) for destination/receiver station
(B). The PMM includes columns and rows. In the example illustrated
in Table 7 (below), the PMM includes three columns as follows: (1)
a column that lists stations including the source/transmitting
station (Z) with identification number z and all other stations
that can potentially engage in peer to peer communication, (2)
another column that lists peer stations (of each station in the
first column) having a high RSS and (3) another column that lists
peer stations (of each station in the first column) having a low
RSS. Although not illustrated, there can be additional columns that
list peer stations (of each station in the first column) having a
medium RSS. An entry is a row of data for a corresponding station
in column 1.
[0196] One example of a PMM is illustrated in Table 7 below. In
this simplified example, the Peer Memory Map (PMM) in Table 7 has
entries for two stations: source/transmitter station (Z) and the
destination/receiver station (B). For destination/receiver station
(B) the PMM includes a list of peer stations (a.sub.1, a.sub.2,
a.sub.3) having a high measured RSS and a list of peer stations
(w.sub.1, w.sub.2, w.sub.3) having a low measured RSS. Similarly,
for the source/transmitting station (Z) the PMM includes a list of
peer stations (x.sub.1, x.sub.2, x.sub.3) having a high measured
RSS and a list of peer stations (y.sub.1, y.sub.2, y.sub.3) having
a low measured RSS. Although not illustrated, the PMM can also
include one entry for each station that can potentially engage in
peer to peer communication. After updating the source transmitter
station PMM entries for z and b in Table 7, in some embodiments the
peers for z and b may also be updated. For example in Table 7 the
PMM entries for stations (x.sub.1, x.sub.2, x.sub.3) all can have
source/transmitter z listed as a high power peer and stations
(a.sub.1, a.sub.2, a.sub.3) can have destination/receiver station b
listed as a high power peer, wherein x.sub.1, x.sub.2, x.sub.3 and
a.sub.1, a.sub.2, a.sub.3 are peer station identification numbers.
(Table 7 does not show the analogous low power peers for stations
(y.sub.1, y.sub.2, y.sub.3) and (w.sub.1, w.sub.2, w.sub.3)).
TABLE-US-00007 TABLE 7 \Peer Memory Map (PMM) Peer Stations Peer
Stations Having Having Station High Measured RSS Low Measured RSS
source/transmitter station (z) x.sub.1 x.sub.2 x.sub.3 y.sub.1
y.sub.2 y.sub.3 destination station (b) a.sub.1 a.sub.2 a.sub.3
w.sub.1 w.sub.2 w.sub.3 . . . STA (x.sub.1) z . . . . . . . . . . .
. . . . STA (x.sub.2) z . . . . . . . . . . . . . . . STA (x.sub.3)
z . . . . . . . . . . . . . . . STA (a.sub.1) b . . . . . . . . . .
. . . . . STA (a.sub.2) b . . . . . . . . . . . . . . . STA
(a.sub.3) b . . . . . . . . . . . . . . . . . .
Generation of Updated Peer Sets
[0197] High RSS peer stations cause the most interference for
nearby receivers, and therefore it is desirable to isolate
transmissions of high RSS peer stations in the time domain by
scheduling transmission of the destination/receiver station (B) so
that they are received at a time when it's high RSS peer stations
are not transmitting.
[0198] The base station receives PRMMs from each station that want
to transmit peer-to-peer (or station-to-station) traffic. Referring
again to FIG. 17, as illustrated at step 1730, the base station
processes the partial resource measurement map (PRMM) 740 provided
in the RMRM 700 along with other PRMMs provided in RMRMs from other
stations to generate or update "peer sets" of stations that have a
high probability of causing near-far issues to each other. In other
words, the base station combines the information from multiple
PRMMs received from different stations to create or update peer
sets.
[0199] In an alternative embodiment, the base station could use
other information to generate updated peer sets. For instance, the
base station could use QoS information about an ongoing
communication session provided in the grant metric response
messages (GMRM) 800 to improve peer sets. For example, if the
receiver reports a medium RSS from another station that is
occurring during its call (via PRMM) and also reports a poor QoS
measurement for that call (via the GMRM), then the base station
could decide to bump up the medium RSS interferer to a high
category (High RSS) based on the impact it is having on the
receiver call.
Marking Timeslots as Excluded or Preferred Based on Transmit and
Receive Peer Sets
[0200] Continuing with FIG. 17, at step 1740, after peer sets are
updated, the base station determines which time slots are excluded
(TS.sub.x) and preferred (TS.sub.p) based on the current station
resource assignments in each time slot, the peer set entry of the
transmitter in the base station PMM and the peer set entry of the
receiver in the base station PMM, and then marks potential time
slots in an uplink portion 450 of the resource allocation map
maintained at the base station.
[0201] Although not illustrated, the base station can then perform
processing during the reactive scheduling method that is similar to
that described above with respect to FIG. 14 to determine which
time slots of the resource allocation map are to be marked excluded
time slots (TS.sub.x) and preferred time slots (TS.sub.p) in
accordance with some embodiments. The base station calculates
excluded time slots (TS.sub.x) and preferred time slots (TS.sub.p)
by comparing stations already in these time slots with transmit
peer set and receive peer set.
[0202] At step 1750, the base station estimates the uplink resource
allocation size (RAS). Specifically, starting with the first
preferred time slot (TS.sub.p) and the first candidate set of
sub-channels, the number of sub-channels required and the transmit
power required are computed. If the number of sub-channels
available in the first preferred time slot (TS.sub.p) is
inadequate, the next preferred time slot (TS.sub.p) is considered
and so on. Any preferences pertaining to horizontal and vertical
striping can be applied.
[0203] At step 1760, the base station re-allocates one or more
uplink resources to the destination/receiver station (B), where the
one or more uplink resources re-allocated to the
destination/receiver station (B) is a "resource allocation" that
can be any combination of one or more preferred time slot (TSP) and
any combination of one or more subcarriers/sub-channels within the
one or more preferred time slots (TS.sub.p). In one embodiment, the
right-most preferred time slot(s) (TS.sub.p) in the UL portion 450
of the resource allocation map, which are also not marked as being
excluded time slots (TS.sub.x), are allocated to the
destination/receiver station (B).
[0204] After the base station re-allocates the uplink resources to
the destination/receiver station (B), at step 1770 the base station
transmits a resource grant message (RGM) to the
destination/receiver station (B) and the source/transmitter station
(Z) to notify them of the uplink resources re-allocated to them.
The source/transmitter station (Z) may then use the allocated
uplink resources specified in the RGM for transmissions to the
destination/receiver station (B).
CONCLUSION
[0205] Traditional OFDMA scheduling solutions for avoiding near-far
problems are base-station centric and do not support peer-to-peer
traffic. The disclosed embodiments enable broadband OFDMA
peer-to-peer communication networks and mesh mobility by using the
MAC layer to avoid scheduling stations that would experience
near-far issues in the same time allocation. The disclosed
embodiments provide a signaling protocol with which the base
station can request peer information from stations and the stations
can appropriately respond to this request. This signaling protocol
allows for both proactive and reactive collection of information.
The disclosed embodiments also provide a seamless mechanism for
transition between a conventional uplink/downlink scheduler and a
scheduler that accommodates significant peer-to-peer traffic. As
traffic changes from BS-station to peer-to-peer, the base station
can adjust the RMIE and/or GMIE to adjust the amount of information
collected by the stations and sent to the base station for creation
of the peer sets needed to prevent near-far scheduling issues.
[0206] In the foregoing specification, specific embodiments have
been described. However, one of ordinary skill in the art
appreciates that various modifications and changes can be made
without departing from the scope of the invention as set forth in
the claims below. Accordingly, the specification and figures are to
be regarded in an illustrative rather than a restrictive sense, and
all such modifications are intended to be included within the scope
of present teachings. The benefits, advantages, solutions to
problems, and any element(s) that may cause any benefit, advantage,
or solution to occur or become more pronounced are not to be
construed as a critical, required, or essential features or
elements of any or all the claims. The invention is defined solely
by the appended claims including any amendments made during the
pendency of this application and all equivalents of those claims as
issued.
[0207] Moreover in this document, relational terms such as first
and second, top and bottom, and the like may be used solely to
distinguish one entity or action from another entity or action
without necessarily requiring or implying any actual such
relationship or order between such entities or actions. The terms
"comprises," "comprising," "has," "having," "includes,"
"including," "contains," "containing" or any other variation
thereof, are intended to cover a non-exclusive inclusion, such that
a process, method, article, or apparatus that comprises, has,
includes, contains a list of elements does not include only those
elements but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. An element
proceeded by "comprises . . . a," "has . . . a," "includes . . .
a," "contains . . . a" does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises, has, includes,
contains the element. The terms "a" and "an" are defined as one or
more unless explicitly stated otherwise herein. The terms
"substantially", "essentially", "approximately", "about" or any
other version thereof, are defined as being close to as understood
by one of ordinary skill in the art, and in one non-limiting
embodiment the term is defined to be within 10%, in another
embodiment within 5%, in another embodiment within 1% and in
another embodiment within 0.5%. The term "coupled" as used herein
is defined as connected, although not necessarily directly and not
necessarily mechanically. A device or structure that is
"configured" in a certain way is configured in at least that way,
but may also be configured in ways that are not listed.
[0208] It will be appreciated that some embodiments may be
comprised of one or more generic or specialized processors (or
"processing devices") such as microprocessors, digital signal
processors, customized processors and field programmable gate
arrays (FPGAs) and unique stored program instructions (including
both software and firmware) that control the one or more processors
to implement, in conjunction with certain non-processor circuits,
some, most, or all of the functions of the method and/or apparatus
described herein. Alternatively, some or all functions could be
implemented by a state machine that has no stored program
instructions, or in one or more application specific integrated
circuits (ASICs), in which each function or some combinations of
certain of the functions are implemented as custom logic. Of
course, a combination of the two approaches could be used.
[0209] Moreover, an embodiment can be implemented as a
computer-readable storage medium having computer readable code
stored thereon for programming a computer (e.g., comprising a
processor) to perform a method as described and claimed herein.
Examples of such computer-readable storage mediums include, but are
not limited to, a hard disk, a CD-ROM, an optical storage device, a
magnetic storage device, a ROM (Read Only Memory), a PROM
(Programmable Read Only Memory), an EPROM (Erasable Programmable
Read Only Memory), an EEPROM (Electrically Erasable Programmable
Read Only Memory) and a Flash memory. Further, it is expected that
one of ordinary skill,
* * * * *
References